DEF 14A of First Interstate Bancsystem Inc, Apr 16, 2026

DEF 14A of First Interstate Bancsystem Inc

Filed Apr 16, 2026 · FY20250000860413-26-000025

Open on EDGAR

  1. Executive Compensation Highlights

    | What We Do... | | What We Do Not Do... | | | ☑ | Emphasize pay for performance | ☒ | Allow for short-selling, hedging, or pledging of Company securities by Company insiders, subject to limited exceptions for certain pre-existing pledging arrangements | | ☑ | Use multiple performance measures and caps on potential incentive payments | ☒ | Allow "single-trigger" accelerated vesting of equity-based awards upon change in control | | ☑ | Engage an independent compensation consultant | ☒ | Grant excessive perquisites | | ☑ | Require minimum equity ownership for directors and executive officers | ☒ | Pay excise tax "gross ups" upon change in control | | ☑ | Maintain a clawback policy | ☒ | Reprice or liberally recycle shares | | ☑ | Discourage excessive risk taking by reserving the right to use discretion in the payout of all incentives | ☒ | Trade in Company securities during designated black-out periods, except under limited circumstances including valid rule 10b5-1 trading plans |

  2. Elements of Total Compensation

    Elements of Total Compensation Using a consistent and calibrated pay-for-performance approach across the Company, we reward results, discourage excessive risk taking, and align short-term and long-term incentives with the generation of shareholder value. To promote a culture that aligns the interests of management with those of our shareholders, our executive compensation program focuses on a mix of fixed and variable compensation. We have three primary elements of compensation: •Base salary: Competitive fixed-base cash compensation determined by individual factors, such as scope of responsibility, experience, and strategic impact. •Short-Term Incentive: Annual performance-based cash incentives aligned with the achievement of individual and Company financial and strategic growth objectives. •Long-Term Incentive: Equity-based incentives to reward and retain executive officers and senior leaders, with an emphasis on long-term Company performance compared to peers.

  3. Continuing Directors Other Than Nominees

    Continuing Directors Other Than Nominees The following table sets forth information as of the date of this proxy statement regarding our directors that are expected to continue to serve on the Board following the date of the annual meeting and who are not up for election at the annual meeting, to whom we refer as our “continuing directors.” Additional biographical information for each of these directors follows below under the caption “Director and Director Nominee Biographies.”

  4. Continuing Directors Other Than Nominees

    | Name | Age | Director Since | Current Class | Term Expires | Principal Occupation | | Renu Agrawal | 62 | 2025 | III | 2027 | Former EVP and COO for Financial Institutions Group, Wells Fargo | | Stephen B. Bowman | 62 | 2021 | I | 2028 | Retired CFO, The Northern Trust Corporation | | John M. Heyneman Jr. | 58 | 2018* | III | 2027 | Managing Partner, Awe LLC and Towanda Investments LLC | | Joyce A. Phillips | 63 | 2021 | I | 2028 | CEO, EqualFuture Corp. | | James A. Reuter | 61 | 2024 | III | 2027 | President and CEO, First Interstate BancSystem, Inc. | | James R. Scott, Jr. | 48 | 2025** | III | 2027 | Managing General Partner, JS Investments LP | | Jeremy P. Scott | 45 | 2025 | I | 2028 | CEO, J&G Brothers Biz, Inc. | | Michael L. Scudder | 65 | 2025 | I | 2028 | Retired Executive Chairman, Old National Bancorp |

  5. Continuing Directors Other Than Nominees

    *In addition, Mr. Heyneman previously served as a director from 1998 to 2004 and from 2010 to 2016. **In addition, Mr. Scott previously served as a director from 2016 to 2022. In addition to Patricia L. Moss, David L. Jahnke (a Class III director with a term expiring at the 2027 annual meeting of shareholders (the “2027 annual meeting”)) and Stephen M. Lacy (a Class I director with a term expiring at the 2028 annual meeting of shareholders (the “2028 annual meeting”)) have each reached the age of 72 and, in accordance with the director retirement policy included in our Corporate Governance Guidelines as further described below, will be deemed to have retired and resigned automatically from the Board immediately prior to the start of the annual meeting. In connection and contemporaneously with the resignations and effective immediately prior to the start of the annual meeting, the size of the Board, and the number of directors in each class of the Board corresponding with the directors resigning from each such class, will be by Board resolution reduced immediately prior to the annual meeting to eliminate any vacancy that would otherwise result on the Board and in each class from their resignations, all in accordance with our bylaws. The following graphic sets forth information regarding our continuing directors and our director nominees for the 2026 annual meeting. For additional information regarding our Board and the directors serving on the Board as of the date of this Proxy Statement, see “Board Structure and Composition” below.

  6. Continuing Directors Other Than Nominees

    | 12 | First Interstate BancSystem, Inc. |

  7. Continuing Directors Other Than Nominees

    | 13 | First Interstate BancSystem, Inc. |

  8. Continuing Directors Other Than Nominees

    Director and Director Nominee Biographies Director Since: February 2021 Chair of the Board Since: May 2024 Career Highlights: Mr. Bowman served as Chief Financial Officer of The Northern Trust Corporation, a global financial institution, from 2014 until his retirement in 2020. As CFO, Mr. Bowman was responsible for the company’s Global Finance function including Controller’s group, Financial Planning and Analysis, Tax, Investor Relations, Treasury, Capital Adequacy, Business Unit Finance, Corporate Real Estate, Procurement, Fee Billing, and Finance Technology. Prior to his CFO role, Mr. Bowman served in various leadership positions at The Northern Trust Corporation, including Chief Human Resources Officer and CEO of Northern Trust’s European region and North American region. Mr. Bowman is a National Trustee of Miami University and serves as the Chair of the Investment Subcommittee. Mr. Bowman also serves on the board of directors for Glenwood Academy, FNZ Trust Company, and Commonwealth Edison Company. Mr. Bowman has a Bachelor’s degree from Miami University, and an M.B.A. from DePaul University.

  9. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Bowman has significant knowledge in the financial services industry, executive management, and legal requirements and duties of public companies. | •Audit Committee (Financial Expert) | •Voya Financial, Inc. (Audit, Risk, and Technology Committee member) |

  10. Continuing Directors Other Than Nominees

    | 14 | First Interstate BancSystem, Inc. |

  11. Continuing Directors Other Than Nominees

    Director Since: November 2024 Career Highlights: Mr. Reuter has been President and Chief Executive Officer of the Company and First Interstate Bank as well as a member of the Board of Directors since November 2024. Mr. Reuter leads with expertise drawn from more than 38 years in the banking industry. Prior to joining the Company, Mr. Reuter was the President and Chief Executive Officer of FirstBank Holding Company of Colorado, one of the largest privately held banks in the nation, from 2017 until his retirement in March 2024. Mr. Reuter started his banking career at FirstBank in 1987 and, prior to CEO, served as the bank’s Chief Operating Officer, overseeing many of the bank’s divisions including: loan/ mortgage operations; information technology (IT); digital banking; payments; business banking; contact center; online account/loan acquisition; marketing; and treasury management. Mr. Reuter has been actively involved in the industry, serving on the Board of Directors of the American Bankers Association (ABA), ABA Government Relations Committee, ABA Payments Systems Advisory Council, and the ABA Venture Investment Committee. He also serves on the Board of Directors for the Mid-Size Bank Coalition of America, and previously served on The Clearing House Real Time Payments Business Committee, the Federal Reserve Bank Faster Payments Task Force Steering Committee, and the Colorado Bankers Association. In addition to industry-related work, Mr. Reuter has served on the boards of numerous nonprofits including: the American Cancer Society of Colorado’s CEOs Against Cancer; Women’s Foundation of Colorado; Special Olympics of Colorado; Ability Connection Colorado; Blind Institute of Technology; and Cerebral Palsy of Colorado. Additionally, Mr. Reuter currently serves as Chair of the First Interstate BancSystem Foundation Board of Directors. Mr. Reuter has a Bachelor’s degree in Finance from Luther College in Decorah, Iowa, and attended the Graduate School of Banking at the University of Wisconsin.

  12. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Reuter has extensive knowledge of key issues, dynamics, and trends affecting the Company, its business, and the banking industry in general. •As President and Chief Executive Officer, Mr. Reuter is also able to provide strategic insight and direction to the Company. | •None | •None |

  13. Continuing Directors Other Than Nominees

    | 15 | First Interstate BancSystem, Inc. |

  14. Continuing Directors Other Than Nominees

    Director Since: August 2025 Career Highlights: From 2006 to 2019, Ms. Agrawal served at Wells Fargo in senior executive roles, including Executive Vice President and Chief Operating Officer for its Financial Institutions Group from 2017 to 2019, Executive Vice President and Head of its International Treasury Management business from 2012 to 2017, and Senior Vice President in Corporate Strategy. Earlier, she was COO of ValleyCrest Companies and of Quisic, a venture-backed EdTech firm, and a Principal at McKinsey & Company. She began her career as a scientist at Polaroid. Ms. Agrawal also serves on the board of Neythri, an organization of South Asian professional women and was named to the NACD Directorship 100 in 2024. Ms. Agrawal serves on the boards of Sunrise Produce, a private equity-owned wholesale distributor, and NMI Holdings, Inc. She also served on the board of Woodruff-Sawyer, one of the largest privately held insurance brokerages, where she chaired the Audit and Risk Committee and served on the Compensation Committee until its acquisition by AJ Gallagher & Co. in April 2025. She was also a director of Allvue Systems, a Vista Equity-owned SaaS company. Ms. Agrawal has a Ph.D. in Materials Science and Engineering and an M.B.A. from MIT, as well as a Bachelor of Technology degree from Indian Institute of Technology in Kanpur, India.

  15. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Ms. Agrawal has extensive leadership experience in the financial services industry. •She also has strong governance, audit, and risk oversight experience as a former public company board member and committee chair. | •Governance and Nominating Committee •Technology, Innovation and Operations Committee | •NMI Holdings, Inc (Audit and Risk Committees) Other Public Company Board Memberships Within the Last Five Years •Luther Burbank Corporation (Audit and Risk and Nominating and Governance Committees) |

  16. Continuing Directors Other Than Nominees

    | 16 | First Interstate BancSystem, Inc. |

  17. Continuing Directors Other Than Nominees

    Director Since: May 2020 Career Highlights: Ms. Cho is a recognized risk expert and has advised financial institutions, technology companies, and government sponsored enterprises on matters relating to enterprise risk management, regulatory compliance, and internal audit. Ms. Cho has served as a consultant to Ludwig Advisors, LLC since 2026. She served as a Senior Advisor at the Boston Consulting Group, a global management consulting firm, from 2021 through 2025. From 2017 to 2020, Ms. Cho served as Advisor to Varo Money, Inc., the nation’s first fintech to receive regulatory approvals to operate as a bank. In that role, Ms. Cho advised the Board, the CEO, and senior management on managing risk in the context of an innovative, digital only business model. From 2005 to 2017, Ms. Cho served in various leadership roles, including Managing Director and the head of the West Coast Practice, at Promontory Financial Group. In that capacity, she was responsible for leading engagements and for advising global financial institutions and leading fintech companies on issues relating to risk management and regulatory strategy. Prior to joining Promontory, Ms. Cho was director at BITS, the technology arm of the Bank Policy Institute. Earlier, Ms. Cho served as Special Advisor to the Vice Chair at the Federal Reserve Board in Washington, D.C. and worked on banking policy issues at the White House Office of Management and Budget. Ms. Cho serves on the Advisory Council at the University of Chicago Harris School of Public Policy. Ms. Cho is a board advisor at Revolut U.S. Ms. Cho has a Bachelor’s degree from Whitman College, and an M.A. from the University of Chicago.

  18. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Ms. Cho has significant knowledge in risk management, and regulatory compliance issues. •She also has knowledge in strategic initiatives and technology innovation, including digitization, in the financial services industry. | •Audit Committee (Financial Expert) •Risk Committee (Chair, Risk Management Expert) | •Globe Life, Inc. (Audit Committee Member) |

  19. Continuing Directors Other Than Nominees

    | 17 | First Interstate BancSystem, Inc. |

  20. Continuing Directors Other Than Nominees

    Director Since: May 2018 Career Highlights: Mr. Heyneman was previously a director from 1998 to 2004 and from 2010 to 2016. Mr. Heyneman is based in Sheridan, Wyoming as the Managing Partner of Awe LLC, and Towanda Investments LLC. Additionally, Mr. Heyneman is Chair of the Padlock Ranch Company, a diversified cow-calf, farm, and feedlot operation based in Dayton, Wyoming. Mr. Heyneman was Executive Director of Plank Stewardship Initiative, a nonprofit organization providing technical solutions to ranchers in the Northern Great Plains. From 2005 to 2010, Mr. Heyneman was involved in economic development and business recruitment in Sheridan, Wyoming. From 1998 to 2009, Mr. Heyneman managed and worked on large cattle ranches on public, private, and tribal lands in northern Arizona, Utah, Montana, and Wyoming. He is an N.A.C.D Leadership Fellow and has completed several executive education programs at the Northwestern University - Kellogg School of Management. Mr. Heyneman has a Bachelor’s degree from Carleton College and an M.A. from Montana State University. Mr. Heyneman is the first cousin of James R. Scott, Jr., and the first cousin once-removed of Jeremy P. Scott. Mr. Heyneman was recommended for Board service by the Scott Family pursuant to the Scott Family Stockholder Agreement (as defined and discussed below).

  21. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Heyneman has executive management and business experience in the agriculture industry. •Mr. Heyneman understands the regional economies and communities the Company serves. •Mr. Heyneman also possesses knowledge of the Company’s unique challenges, regulatory environment, and history because of his years of service to the Company. | •Governance and Nominating Committee •Technology, Innovation and Operations Committee | •None |

  22. Continuing Directors Other Than Nominees

    | 18 | First Interstate BancSystem, Inc. |

  23. Continuing Directors Other Than Nominees

    Director Since: May 2017 Career Highlights: Prior to his retirement in 2020, Mr. Johnson was President and Chief Executive Officer of United Heritage Mutual Holding Company since 2001, and United Heritage Financial Group and United Heritage Life Insurance Company, which are insurance, annuity, and financial products companies, since 1999. Mr. Johnson served as President and Chief Executive Officer of United Heritage Financial Services, a broker-dealer, from 1994-1998 and served as General Counsel of United Heritage Mutual Holding Company and its predecessor and certain of its affiliates from 1983 to 1999. Mr. Johnson also serves on the boards of Northwest Nazarene University Foundation and Fidelity Security Assurance Company. Mr. Johnson is a former trustee of the Public Employees Retirement System of Idaho and is a member of the Idaho Citizens’ Committee on Legislative Compensation, appointed by the Idaho Supreme Court. Mr. Johnson has a Bachelor’s degree from Northwest Nazarene College, and a Juris Doctor from the University of Idaho.

  24. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Johnson has significant experience in the insurance industry and deep expertise in risk management issues. • A licensed Idaho attorney and former General Counsel, he has also served as CEO of insurance and financial services businesses, including a broker-dealer, providing legal, regulatory oversight, and corporate governance expertise. • Public company experience as Chair and a director of IDACORP, Inc./Idaho Power Company. Previously, director at Bank of the Cascades. | •Risk Committee (Risk Management Expert) •Audit Committee (Financial Expert) | •IDACORP, Inc. (Board Chair and Corporate Governance & Nominating Committee Chair) |

  25. Continuing Directors Other Than Nominees

    | 19 | First Interstate BancSystem, Inc. |

  26. Continuing Directors Other Than Nominees

    Director Since: February 2021 Career Highlights: During a 30-year career, Ms. Phillips has led significant businesses including retail banking, credit cards, insurance, and wealth management. Ms. Phillips is Founder and CEO of EqualFuture Corp., a FinTech startup based in San Francisco, that delivers affordable personal financial wellness via a SaaS model to individuals and businesses. Prior executive roles include Group Managing Director M&A, Chief Marketing and Innovation Officer, and CEO of Australia and New Zealand Banking Group Limited’s (ANZ) Global Wealth Division. Prior to joining ANZ, Ms. Phillips was President and Chief Operating Officer at American Life Insurance Company (ALICO), a global subsidiary of American International Group, Inc. Ms. Phillips previously held senior executive roles for Citigroup including Head of International Retail Banking. In that role she was responsible for strengthening product and distribution in 42 countries. Ms. Phillips was included in the U.S. Banker "25 Most Powerful Women in Banking and Finance" list multiple years and named one of the Top 100 FinTech leaders in Asia. Ms. Phillips also serves on various non-profit boards including Girls Inc. NYC, the Smithsonian National Board, and the First Interstate BancSystem Foundation Board of Directors. Ms. Phillips has a Bachelor’s degree from the University at Buffalo and an M.B.A. from NYU Stern School of Business.

  27. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Ms. Phillips has significant experience in financial services and FinTech industries. •Ms. Phillips also has knowledge of the regulatory environment. | •Technology, Innovation and Operations Committee (Chair) •Compensation and Human Capital Committee | •None Other Public Company Board Memberships Within the Last Five Years •Katapult Holdings, Inc. (Nominating and Corporate Governance (Chair) and Audit Committees) •Western Union Company (Compensation and ESG Committees) |

  28. Continuing Directors Other Than Nominees

    | 20 | First Interstate BancSystem, Inc. |

  29. Continuing Directors Other Than Nominees

    Director Since: February 2022 Career Highlights: Mr. Rykhus retired as President and Chief Executive Officer of Raven Industries in 2021 after serving in that role for 11 years and for the company for 31 years in leadership positions. Raven was a publicly held corporation that serves the precision agriculture, high performance specialty films, and situational awareness markets, and was acquired by CNHi at the time of Mr. Rykhus’ retirement as CEO. Under Mr. Rykhus’s leadership, the company transformed from an industrial company to a growing technology driven organization. Mr. Rykhus currently serves on the boards of directors of several non-profit organizations and advises other businesses. Mr. Rykhus has a Bachelor’s degree from University of Minnesota, and an M.B.A. from Colorado State University.

  30. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Rykhus brings to the Board 32 years of leadership experience and his many years of experience as a director and past Audit Committee member of Great Western Bancorp. •As the leader of a publicly held company, Mr. Rykhus also brings several years of public company corporate governance experience to the Board. | •Compensation & Human Capital Committee •Governance and Nominating Committee (Chair) | •None Other Public Company Board Memberships Within the Last Five Years •Raven Industries •Great Western Bancorp (Compensation (Chair) Executive, Audit, and Governance committees) |

  31. Continuing Directors Other Than Nominees

    | 21 | First Interstate BancSystem, Inc. |

  32. Continuing Directors Other Than Nominees

    Director Since: May 2025 Career Highlights: Mr. Scott previously served as a director of the Board from 2016 to 2022, fulfilling roles on the Governance and Nominating Committee, the Risk Committee, and the Technology, Innovation, and Operations Committee. Mr. Scott currently serves as the Managing General Partner of JS Investments LP. Prior to May 2025, Mr. Scott served as Vice President and Commercial Group Manager of First Interstate Bank in Denver, Colorado, a role he assumed in 2022. Also within the Company, he served as a Commercial Loan Manager in Ashland, Oregon from 2017 to 2019 and Vice President in the Missoula, Montana Commercial Banking group from 2014 to 2017. Prior to joining First Interstate Bank, Mr. Scott was a credit analyst and commercial banker with Citywide Banks of Denver, Colorado, from 2010 to 2014. Additionally, Mr. Scott serves on the Padlock Ranch Company Board and is a director of the Homer and Mildred Scott Foundation. Mr. Scott has a Bachelor’s degree from the University of Colorado-Leeds School of Business as well as an MBA and Master of Science in Finance from the University of Denver- Daniels College of Business. Mr. Scott is the first cousin of John M. Heyneman, Jr., and the first cousin-once-removed of Jeremy P. Scott. He was recommended for Board service by the Scott Family pursuant to the Scott Family Stockholder Agreement.

  33. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •Mr. Scott has significant banking experience as a result of his years of service to the Company, other banking organizations as identified above, and other family- related businesses. | •Technology, Innovation and Operations Committee •Risk Committee | •None |

  34. Continuing Directors Other Than Nominees

    | 22 | First Interstate BancSystem, Inc. |

  35. Continuing Directors Other Than Nominees

    Director Since: May 2025 Career Highlights: From 2023 until joining the Board, Mr. Scott served as a Board Observer pursuant to the Scott Family Stockholder Agreement. Mr. Scott serves as Co-Founder and Chief Executive Officer of J&G Brothers Biz, Inc., an e-commerce company that currently sells 500 unique products in 15 countries. Mr. Scott also serves as an owner and as a director of GP87 Inc., an international manufacturer of snowboard, ski, and surf equipment. Over the course of his career, Mr. Scott has founded or co-founded three businesses that, at their peaks, have collectively employed over 300 employees in total. Early in his career, Mr. Scott was employed by the Company in various roles, including as a credit analyst. Additionally, Mr. Scott serves on the boards of directors of the First Interstate BancSystem Foundation, TRV Scholarship Fund, H&M Scott Foundation, D&J Scott Foundation, and Padlock Ranch Company. Mr. Scott has a Bachelor’s degree from Linfield University. Mr. Scott is the first cousin once removed of James R. Scott, Jr., and John M. Heyneman, Jr. Mr. Scott was recommended for Board service by the Scott Family pursuant to the Scott Family Stockholder Agreement.

  36. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Scott brings to the Board business and leadership experience derived from founding multiple businesses. •He also has an understanding of the regional economies and communities the Company serves and an understanding of the Company’s business derived from serving as Board observer and as prior employee. | •Compensation and Human Capital Committee •Governance & Nominating Committee | •None |

  37. Continuing Directors Other Than Nominees

    | 23 | First Interstate BancSystem, Inc. |

  38. Continuing Directors Other Than Nominees

    Director Since: August 2025 Career Highlights: Mr. Scudder retired as Executive Chairman of the Board of Old National Bancorp in January 2024, following a 38-year career with Old National Bancorp and First Midwest Bancorp, both of which were publicly traded institutions. He served as Executive Chairman of Old National Bancorp following its merger with First Midwest Bank Corp. in February 2022 and previously served as President and Chief Executive Officer of First Midwest Bank Corp. from 2007 to 2022 and Chief Financial Officer from 2002 to 2007, and, prior to 2002, held enterprise-wide senior leadership responsibilities across financial, operational, risk, and governance functions. Mr. Scudder is a member of the Board of Trustees of DePaul University and currently serves as its Chairman. He is also the Vice Chairman of the Board of Directors for Silver Cross Hospital. He has and continues to serve on a number of organizations and affiliations within the financial services industry and the broader community. Mr. Scudder holds a Bachelor’s degree from Illinois Wesleyan University as well as a Master’s degree from DePaul University.

  39. Continuing Directors Other Than Nominees

    | Qualifications | Committee Memberships | Additional Current Public Company Board Memberships | | •As identified by the Board, Mr. Scudder brings extensive experience in public company governance, operations, financial reporting, regulatory oversight, risk management, and capital markets. •Mr. Scudder is a Certified Public Accountant and contributes significant financial and accounting expertise to the Board. | •Audit Committee •Risk Committee | •None Other Public Company Board Memberships Within the Last Five Years •Old National Bancorp (Executive Chair) •First Midwest Bancorp (Chairman and CEO) |

  40. Continuing Directors Other Than Nominees

    | 24 | First Interstate BancSystem, Inc. |

  41. Continuing Directors Other Than Nominees

    Corporate Governance

  42. Political Contributions and Public Advocacy

    | Compensation and Human Capital Committee | | | | Meetings Held in 2025: 5 | Additional Members: Patricia L. Moss*, Joyce A. Phillips, Daniel A. Rykhus, and Jeremy P. Scott | Independence: Each member of this committee is independent under applicable NASDAQ Marketplace Rules | | Key Committee Responsibilities: | | | | •Reviews and approves goals relevant to compensation for executive officers and evaluates the effectiveness of our compensation practices in achieving Company objectives, encouraging behaviors consistent with our values, and aligning performance objectives. | | | | •Reviews and approves the compensation of our non-CEO Named Executive Officers (“NEOs”), recommends for Board approval of CEO compensation, and oversees succession planning for all executive officers. In addition, the Committee recommends compensation for Board members. | | | | •Oversees the Company’s equity and incentive compensation plans and operation of compensation programs affecting the Company’s employees generally. Approves equity awards granted to the non-CEO NEOs and recommends Board approval of CEO equity awards. The Compensation and Human Capital Committee has delegated authority to our CEO to make awards to employees who are not NEOs. | | | | •Provides oversight of the Company’s talent management, development, and related programs, including programs related to diversity, opportunity, and inclusion. | | | | •Oversees the Company’s CEO and executive succession planning. | | | | Compensation Consultant. The Compensation and Human Capital Committee (“Compensation Committee”) has retained the services of Pearl Meyer & Partners (“Pearl Meyer”), a compensation consulting firm, to assist with its executive compensation review and to provide competitive market data. A consultant from Pearl Meyer generally attends the Compensation Committee meetings at which executive officer compensation is discussed and provides information, research, and analysis pertaining to executive compensation and updates on market trends as requested by the Compensation Committee. In connection with its engagement of Pearl Meyer, the Compensation Committee considered various factors bearing upon Pearl Meyer’s independence including, but not limited to, the amount of fees received by Pearl Meyer from the Company, Pearl Meyer’s policies and procedures designed to prevent conflicts of interest, and the existence of any business or personal relationship that could impact Pearl Meyer’s independence. After reviewing these and other factors, the Compensation Committee determined that Pearl Meyer was independent and that its engagement did not present any conflicts of interest. Pearl Meyer does not provide executive compensation services to the Company. The Compensation Committee sets compensation levels based on the skills, experience, and achievements of each executive officer, considering market analysis and input provided by Pearl Meyer and the compensation recommendations of our Chief Executive Officer, except with respect to his own position. The Compensation Committee believes that input from both Pearl Meyer and our Chief Executive Officer provides useful information and perspective to assist the Compensation Committee in determining the appropriate compensation. *Each of Mr. Lacy and Ms. Moss will leave the Committee when their service on the Board ends immediately prior to the annual meeting. | | | | Compensation and Human Capital Committee Interlocks and Insider Participation: | | | | •No members of the Compensation Committee who served during 2025 were officers or employees of the Company during the year, or were former officers of the Company, or had any relationship requiring disclosure under the caption "Certain Relationships and Related Party Transactions" included below in this proxy statement. | | | | •No executive officer of the Company served on the compensation committee or board of directors of another company that had an executive officer who served on the Company's Compensation Committee or Board. | | |

  43. Effective Time; Filing of Amendment

    Director Compensation We use a combination of cash and equity-based incentive compensation to attract and retain qualified candidates to serve on our Board. In setting director compensation, we consider the significant amount of time that directors expend in fulfilling their duties as well as the skill level required by us with respect to members of the Board. Annual non-employee director compensation is based upon a service year beginning on June 1 and ending on May 31 of each year. For the 2025-2026 service year, each non-employee director, other than the Chair of the Board, is entitled to receive an annual retainer valued at $140,000, of which approximately $80,000 was paid in the form of restricted stock units (“RSUs”) on June 1, 2025 and the remaining approximately $60,000 is payable on a quarterly basis in the form of cash or RSUs at the director's election. For his services as Chair of the Board for the 2025-2026 service year, Stephen B. Bowman is entitled to receive an annual retainer of $230,000, of which approximately $130,000 was paid in the form of RSUs on June 1, 2025 and the remaining approximately $100,000 is payable on a quarterly basis in the form of cash or RSUs at his election. The retainer paid to the Chair of the Board is in lieu of all committee fees and other retainers described below. The retainer paid to the Chair of the Board recognizes the Chair’s work in providing an interface between the Board and our management, oversight of strategic planning, leadership of the Board, executive succession planning, and community visibility. Committee members and committee chairpersons retainer fees are as follows:

  44. Director Compensation Table

    Director Compensation Table

  45. Director Compensation Table

    | Name | Fees Earned or Paid In Cash(1) | Stock Awards(2)(3) | All Other Compensation(4) | Total | | Stephen B. Bowman | $87,500 | $130,000 | $12,748 | $230,248 | | Renu Agrawal(5) | 37,500 | 60,000 | 10,000 | 107,500 | | Alice S. Cho | 94,375 | 80,000 | 6,666 | 181,041 | | John M. Heyneman, Jr. | 77,875 | 80,000 | 14,120 | 171,995 | | David L. Jahnke | 94,375 | 80,000 | 5,666 | 180,041 | | Dennis L. Johnson | 80,000 | 80,000 | 10,000 | 170,000 | | Stephen M. Lacy | 91,250 | 80,000 | 15,666 | 186,916 | | Patricia L. Moss | 77,500 | 80,000 | 5,666 | 163,166 | | Joyce A. Phillips | 89,750 | 80,000 | 15,666 | 185,416 | | James A. Reuter(6) | — | — | — | — | | Daniel A. Rykhus | 94,375 | 80,000 | 15,666 | 190,041 | | James R. Scott, Jr.(7) | 58,125 | 80,000 | 5,000 | 143,125 | | Jeremy P. Scott(8) | 58,125 | 80,000 | 10,000 | 148,125 | | Michael L. Scudder(9) | 40,000 | 60,000 | — | 100,000 | | Frances P. Grieb(10) | 24,375 | — | 12,410 | 36,785 | | Thomas E. Henning(10) | 19,375 | — | 15,666 | 35,041 | | James R. Scott(10) | 19,375 | — | 5,666 | 25,041 | | Jonathan R. Scott(10) | 15,625 | — | 6,729 | 22,354 |

  46. Director Compensation Table

    (1) The amounts listed in this column include the retainer and committee fees paid by the Company to the non-employee directors in the 2025 calendar year. Committee assignments, retainers, and committee fees are set for the period of June 1 through May 31. The amount for Mr. Rykhus includes $30,000 in cash retainer fees in which Mr. Rykhus elected to receive in the form of RSUs issued on June 1, 2025 with a grant date fair market value of $27.15 per share. (2) The amounts reflect the aggregate grant date fair value of RSUs granted to our non-employee directors in June 2025 computed in accordance with FASB ASC Topic 718. The grant date fair value of RSUs awarded in 2025 utilized the closing price of a share of our common stock on the trading day immediately prior to the grant date of $27.15, except for Mr. Scudder who was granted RSUs on August 27, 2025 with a grant date fair market value of $31.93 per share, and Ms. Agrawal who was granted RSUs on September 5, 2025 with a grant date fair market value of $32.83 per share. The RSUs granted in 2025 vest on June 1, 2026, subject to the director’s provision of continuous service to the Company through the date of the annual meeting on May 27, 2026. (3) As of December 31, 2025, each non-employee director held 2,946 unvested RSUs, other than Mr. Bowman who held 4,788, Mr. Rykhus who held 4,050, Ms. Agrawal who held 1,827, and Mr. Scudder who held 1,879 unvested RSUs. (4) The amounts in this column reflect (1) the amount of accrued cash dividend equivalent payments made upon the vesting of outstanding equity awards and delivery of shares underlying such equity awards in 2025, which had been granted in prior years, and (2) for certain of the directors, matching contributions made under First Interstate BancSystem Foundation’s Matching Gift program as follows: Ms. Agrawal, $10,000; Ms. Cho, $1,000; Mr. Heyneman, $8,454; Mr. Johnson, $10,000; Mr. Lacy, $10,000; Ms. Phillips, $10,000; Mr. Rykhus, $10,000; Mr. James Scott Jr., $5,000; Mr. Jeremy Scott, $10,000; and Mr. Henning, $10,000. (5) Ms. Agrawal was appointed to the Board on August 29, 2025 and received a pro-rated amount of retainer and committee fees. (6) Mr. Reuter received no separate compensation for serving as a director, but was compensated in his capacity as President and Chief Executive Officer included herein in the “Summary Compensation Table.” (7) Mr. James R. Scott, Jr., who was appointed to the Board on May 21, 2025, was employed by the Bank as a Vice President and Commercial Group Manager until his voluntary retirement in May 2025 and received approximately $117,367 in total compensation (including salary) for his services as an employee prior to his retirement. Such employee compensation is not included in the Director Compensation Table above, which reflects only compensation paid to Mr. Scott for his service as a director. (8) Mr. Jeremy Scott was elected to the Board at the 2025 annual meeting held in May 2025. (9) Mr. Scudder was appointed to the Board on August 13, 2025 and received a pro-rated amount of retainer and committee fees. (10) Ms. Grieb, Mr. Henning, Mr. James R. Scott, and Mr. Jonathan Scott’s service on the Board ended as of the 2025 annual meeting held in May 2025.

  47. Director Compensation Table

    | 41 | First Interstate BancSystem, Inc. |

  48. 2025 Short-Term Incentive Plan Design

    2025 Short-Term Incentive Plan Design For 2025, the Compensation Committee approved one change to the quantitative performance metrics under our 2025 Short-Term Incentive Plan (“2025 STI Plan”). Adjusted Non-Interest Expenses/Total Average Assets metric (weighted 25%) was replaced with Adjusted Efficiency Ratio (weighted 25%). Other than this substitution, the 2025 STI Plan retained the same quantitative performance metrics and relative weightings as the 2024 Short-Term Incentive Plan (“2024 STI Plan”), as reflected in the table below.

  49. 2025 Short-Term Incentive Plan Design

    | 2024 STI Plan | 2025 STI Plan | | Adjusted Pre-Provision Net Revenue (“PPNR”) per Share (50%) | Adjusted PPNR per Share (50%) | | Adjusted Non-Interest Expenses/Total Average Assets (25%) | Adjusted Efficiency Ratio (25%) | | Relative Non-performing Assets (“NPAs”)/Total Assets (25%) | Relative NPAs/Total Assets (25%) |

  50. 2025 Short-Term Incentive Plan Design

    Management proposed the modification, and the Compensation Committee determined that the revised metric better aligns with the Company’s operating priorities for 2025. Additional details are provided below under the heading “2025 STI Plan”.

  51. 2025 STI Plan Funding Results

    2025 STI Plan Funding Results Based on the Company’s performance for 2025, the quantitative performance metrics achieved funding at 87% of target. Additional details regarding the STI payments are provided below under the heading “2025 STI Plan - Company Performance-Based Quantitative Results”.

  52. 2025 STI Plan Funding Results

    | 52 | First Interstate BancSystem, Inc. |

  53. 2025 Long-Term Incentive Plan Design

    2025 Long-Term Incentive Plan Design For 2025, our LTI award mix remained unchanged at 60% performance restricted stock units (“PRSUs”) and 40% time-based restricted stock units (“RSUs”). Management recommended, and the Compensation Committee approved, one change to the performance metrics applicable to the performance awards granted under our 2025 Long-Term Incentive Plan (“2025 LTI Plan”). The Core Return on Average Equity (“Core ROAE”) metric (50%) was replaced with Core Return on Average Tangible Common Equity (“Core ROATCE”) (50%). Other than this substitution, the quantitative performance metrics and relative weightings applicable to the PRSUs under the 2025 LTI Plan remained unchanged from our 2024 Long-Term Incentive Plan (“2024 LTI Plan”), as summarized in the table below.

  54. 2025 Long-Term Incentive Plan Design

    | 2024 LTI Plan | 2025 LTI Plan | | Total Shareholder Return (50%) | Total Shareholder Return (50%) | | Core Return on Average Equity (“Core ROAE”) (50%) | Core Return on Average Tangible Common Equity (“Core ROATCE”) (50%) |

  55. 2025 Long-Term Incentive Plan Design

    Additional details of our 2025 LTI Plan are provided under the heading “2025 Long-Term Incentive Plan”.

  56. 2023 Performance Award Vesting

    2023 Performance Award Vesting The PRSUs granted to our NEOs in 2023 under our 2023 LTI Plan were scheduled to vest on March 15, 2026 based on the performance measurement period that was completed on December 31, 2025. Neither of the performance metrics achieved threshold performance, which resulted in none of the 2023 PRSUs vesting. Details are provided under the heading “2023 Long-Term Incentive Performance Results”.

  57. Employment Transition of Lorrie F. Asker

    | What We Do... | | What We Do Not Do... | | | ☑ | Emphasize pay for performance | ☒ | Allow for short-selling, hedging, or pledging of Company securities, subject to limited exceptions for certain pre-existing pledging arrangements | | ☑ | Use multiple performance measures and caps on potential incentive payments | ☒ | Allow "single-trigger" accelerated vesting of equity-based awards upon change in control | | ☑ | Engage an independent compensation consultant | ☒ | Grant excessive perquisites | | ☑ | Require minimum equity ownership for directors and executive officers | ☒ | Pay excise tax "gross ups" upon change in control | | ☑ | Maintain a clawback policy | ☒ | Reprice or liberally recycle shares | | ☑ | Discourage excessive risk taking by reserving the right to use discretion in the payout of all incentives | ☒ | Trade in Company securities during designated black-out periods, except under limited circumstances including valid rule 10b5-1 trading plans |

  58. Role of Compensation Consultants

    Role of Compensation Consultants The Compensation Committee has retained Pearl Meyer, an independent compensation consulting firm, to assist with its review of executive compensation and to provide competitive market data. A consultant from Pearl Meyer attends Compensation Committee meetings at which executive officer compensation is discussed and provides research, analysis, and updates on market trends at the request of the Compensation Committee. The Compensation Committee sets compensation levels based on the skills, experience, and performance achievements of each executive officer, taking into account market analysis and input provided by Pearl Meyer, as well as the CEO’s recommendations (except with respect to his own compensation). In connection with its engagement of Pearl Meyer, the Compensation Committee evaluates the firm’s independence, considering factors such as the amount of Pearl Meyer’s fees paid by the Company, Pearl Meyer’s policies and procedures designed to prevent conflicts of interest, and any business or personal relationship that could affect Pearl Meyer’s independence. After reviewing these and other relevant factors, the Compensation Committee determined that Pearl Meyer was independent and that its engagement did not present any conflicts of interest.

  59. Role of Compensation Consultants

    | 56 | First Interstate BancSystem, Inc. |

  60. Role of Peer Group Market Analysis

    Role of Peer Group Market Analysis The Compensation Committee, with input and guidance from Pearl Meyer, evaluates the competitiveness of executive officer compensation using data from a comparative peer group. The peer group consists of publicly traded commercial banks and bank holding companies with geographic, operational, and business model characteristics similar to the Company and total assets ranging between 60% and 200% of the Company’s total assets. The Compensation Committee reviews and approves the peer group on an annual basis. The following companies were approved by the Compensation Committee for purposes of setting compensation levels for 2025 (reflecting the addition of Atlantic Union Bankshares Corporation, Eastern Bankshares, Inc., and United Community Banks, Inc. and the removal of PacWest Bancorp, as compared to the peer group used for purposes of setting compensation levels for 2024):

  61. Role of Peer Group Market Analysis

    | Ameris Bancorp | Hancock Whitney Corporation | | Associated Banc-Corp | Old National Bancorp | | Atlantic Union Bankshares Corporation | Pacific Premier Bancorp, Inc. | | BankUnited, Inc. | Pinnacle Financial Partners, Inc. | | Cadence Bank | Prosperity Bancshares, Inc. | | Columbia Banking System, Inc. | Simmons First National Corporation | | Commerce Bancshares, Inc. | SouthState Corporation | | Eastern Bankshares, Inc. | UMB Financial Corporation | | F.N.B Corporation | United Bankshares, Inc. | | Fulton Financial Corporation | United Community Banks, Inc. | | Glacier Bancorp, Inc. | Valley National Bancorp |

  62. Base Salaries

    Base Salaries Our base salaries are intended to provide a competitive fixed level of compensation to support the recruitment and retention of executive talent. The Compensation Committee annually reviews NEO base salaries relative to peer benchmarking data provided by Pearl Meyer. As described above under “2025 Compensation Highlights—Compensation Opportunities,” in late 2023, the Compensation Committee undertook a two-year effort to better align non-CEO NEO target total direct compensation with competitive market practices. In 2024, base salaries for non-CEO NEOs remained unchanged (with the exception of an increase approved in August 2024 for Ms. Robbins to reflect additional responsibilities added to her role as Chief Operations Officer), while adjustments to target incentive opportunities were used to begin addressing identified market gaps. In January 2025, following its review of updated peer benchmarking data, the Compensation Committee approved increases to base salaries for non-CEO NEOs to further align target total direct compensation with market practices. In determining base salary levels, the Compensation Committee considers each NEO’s total target compensation market positioning, as well as individual factors such as performance, scope of responsibility, experience, and strategic impact. The following table shows base salaries for each NEO for 2024 and 2025.

  63. Short-Term Incentives

    Short-Term Incentives Consistent with our pay-for-performance philosophy, our executive officers are eligible to earn annual short-term incentives tied to Company performance-based quantitative metrics and individual performance-based qualitative measures. The Compensation Committee approves: •Target STI opportunity for each NEO, expressed as a percentage of base salary; •financial metrics used each year to determine Company performance-based funding; and •Company-wide and/or individual performance-based qualitative discretionary adjustments to the quantitative funding results. The Compensation Committee believes individual performance should be considered in determining STI awards. Accordingly, the CEO may recommend to the Compensation Committee adjustments to a non- CEO NEO’s STI award based on individual performance, in lieu of the Company performance quantitative funding percentage. Pursuant to the terms of the annual STI Plan and authority granted under its charter, the Compensation Committee retains discretion to adjust NEO payouts as it deems appropriate. The Compensation Committee approves the STI awards for non-CEO NEOs, and the Board approves the STI award for the CEO.

  64. Short-Term Incentives

    | 58 | First Interstate BancSystem, Inc. |

  65. 2025 STI Plan

    2025 STI Plan The quantitative Company performance component of the 2025 STI Plan for the NEOs was based on three metrics: two tied to our 2025 financial performance relative to initial budget expectations; and one credit quality metric measured relative to peer performance, as follows:

  66. 2025 STI Plan

    | Metric | Weight | Description | | Adjusted Pre-Provision Net Revenue (PPNR) per Share | 50% | Adjusted PPNR per Share is calculated as Adjusted PPNR divided by weighted-average diluted shares outstanding. Adjusted PPNR, for purposes of this calculation, is defined as net revenue, adjusted to exclude realized securities gains or losses, amortization of intangibles, OREO expenses, short-term incentive accrued in excess of budget, and non- recurring items, including, but not limited to, net gains on disposition of premises and equipment, FDIC special assessments and certain severance costs. | | Adjusted Efficiency Ratio | 25% | Adjusted Efficiency Ratio is calculated as adjusted non- interest expense divided by adjusted operating revenue. For purposes of this calculation, the numerator and denominator are adjusted, as applicable, for the same items as described for the Adjusted PPNR per Share metric above. | | Relative Non-performing Assets (NPAs) as a percentage of Total Assets | 25% | Relative NPAs / Total Assets is based on a percentile ranking of Company results compared to the companies that comprise the KBW Regional Banking Index (KRX Index). For this purpose, NPAs are calculated in accordance with GAAP and include non-performing loans and other real estate owned (OREO). |

  67. 2025 STI Plan

    The performance-based metrics and goals are established in the first quarter at threshold, target, and maximum levels. Funding for performance between threshold and maximum levels is determined using linear interpolation, as outlined in the chart below. Results for each metric are calculated independently, weighted, and then aggregated to determine the overall Company funding result.

  68. 2025 STI Plan

    | Performance Level | Payout Range | | Below Threshold | 0% | | Threshold | 50% | | Target | 100% | | Maximum | 200% |

  69. 2025 STI Plan

    | 59 | First Interstate BancSystem, Inc. |

  70. 2025 STI Plan - Company Performance-Based Quantitative Results

    2025 STI Plan - Company Performance-Based Quantitative Results Goals and performance outcomes for the funding of the 2025 STI Plan were as follows:

  71. 2025 STI Plan - Company Performance-Based Quantitative Results

    | Performance Measure | Weight | Threshold Performance | Target Performance | Maximum Performance | Performance Result | Weighted Payout % | | Adjusted PPNR per Share | 50% | $3.05 | $3.81 | $4.95 | $3.66 | 45% | | Adjusted Efficiency Ratio | 25% | 64.17% | 62.17% | 60.17% | 62.25% | 25% | | Relative NPAs/Total Assets | 25% | 25th percentile | 50th percentile | 75th percentile | 34th percentile | 17% | | 2025 STI Plan Funding Results | | | | | | 87% |

  72. 2025 STI Plan - Target Opportunities and Payouts

    2025 STI Plan - Target Opportunities and Payouts The following table shows the 2025 STI Plan target award opportunities, and the amounts approved by the Compensation Committee for our non-CEO NEOs and by the Board for our CEO. STI awards were paid out based solely on the quantitative results as there were no individual performance adjustments applied.

  73. 2025 STI Plan - Target Opportunities and Payouts

    | | | Target Payout Opportunity | | Actual Payouts | | | Officer | 2025 Base Salary ($) | Target (%) | Target Amount ($) | Payout (%) | Payout Amount ($) | | James A. Reuter | 1,000,000 | 120 | 1,200,000 | 87 | 1,044,000 | | David P. Della Camera(1) | 500,000 | 70 | 350,000 | 87 | 304,500 | | Kristina R. Robbins | 460,000 | 70 | 322,000 | 87 | 280,140 | | Kirk D. Jensen | 453,643 | 70 | 317,550 | 87 | 276,269 | | Lori A. Meyer | 330,000 | 70 | 231,000 | 87 | 200,970 | | Marcy D. Mutch(2) | 566,951 | 80 | 387,417 | 87 | 337,052 | | Lorrie F. Asker(3) | 484,000 | 80 | 387,200 | 87 | 336,864 |

  74. 2025 STI Plan - Target Opportunities and Payouts

    (1) Mr. Della Camera’s 2025 STI Plan target opportunity (and the Target Amount shown) was based on his annualized 2025 base salary as CFO ($500,000). (2) Pursuant to the Mutch Transition Agreement, Ms. Mutch was entitled to continue to participate in the 2025 STI Plan based on her original 2025 STI Plan target opportunity (80%) for the portion of 2025 through May 31, 2025, with any payout prorated for the applicable period, and thereafter at 75% of her original 2025 STI Plan target opportunity during the Executive Advisor Period through December 31, 2025, with any payout prorated for the Executive Advisor Period, subject to Company and individual performance. (3) Pursuant to the Asker Transition Agreement, Ms. Asker was entitled to continue to participate in the 2025 STI Plan based on her original 2025 STI Plan target opportunity, subject to Company and individual performance.

  75. Long-Term Incentives

    Long-Term Incentives We believe long-term equity incentive compensation encourages a focus on the long-term performance of the Company. Under the Company's 2023 Equity and Incentive Plan, as amended (the “2023 Plan”), awards are granted to enhance our ability to attract, retain, and motivate executives by providing equity ownership opportunities and performance-based incentives that align their interests with those of our shareholders. The Compensation Committee annually engages Pearl Meyer to conduct a market review of the design of our LTI Plan relative to our peer group. The Compensation Committee reviews and recommends for Board approval the CEO’s total compensation, including long-term incentives, and reviews and approves the total compensation of the non-CEO NEOs, including long-term incentives. The Compensation Committee has delegated to the CEO, subject to certain terms and limitations, the authority to grant equity awards to employees who are not NEOs. Additional information regarding our equity compensation plans is provided under “Equity Compensation Plans” included in this proxy statement.

  76. Long-Term Incentives

    | 60 | First Interstate BancSystem, Inc. |

  77. 2025 Long-Term Incentive Plan

    2025 Long-Term Incentive Plan Incentives under our LTI Plan are issued to our executives in the form of equity consisting of RSUs and PRSUs as follows:

  78. 2025 Long-Term Incentive Plan

    | Type | Weight | Description | | Performance Restricted Stock Units (PRSUs) | 60% | •Relative Performance: Based on results compared to peers in the KBW Regional Banking Index (KRX Index) •Performance Metrics: ◦50% Core ROATCE ◦50% Total Shareholder Return •Performance Measurement Period: 3 years (1/1/2025-12/31/2027) •Vesting: 3 years after grant date, subject to continued employment and performance criteria •Payout range: 50-200% of target; if minimum performance thresholds are not met, 0% of the award will vest | | Restricted Stock Units (RSUs) | 40% | •Vesting: Time-based vesting 1/3 each year for 3 years, subject to continued employment |

  79. 2025 Long-Term Incentive Plan

    For the PRSUs, performance goals and payout ranges are established at threshold, target, and maximum levels. The payout percentage is determined based on the Company’s percentile ranking relative to its peers over the three-year performance period, for each of the selected performance measures, as illustrated in the chart below. Performance results between threshold and maximum performance levels are determined using linear interpolation. Results are calculated independently for each metric, weighted according to their respective weightings, and aggregated to determine the total payout percentage on the award.

  80. 2025 Long-Term Incentive Plan

    | Performance Level | Percentile Ranking | Payout Range | | Below Threshold | Below 25th percentile | 0% | | Threshold | 25th percentile | 50% | | Target | 50th percentile | 100% | | Maximum | 90th percentile | 200% |

  81. 2025 Long-Term Incentive Plan

    Core ROATCE is calculated as Core Income divided by average tangible common shareholders’ equity. Core Income, for purposes of this calculation has the same meaning as defined by S&P Global (or its successor), and generally means net income after taxes and before extraordinary items, less net income attributable to noncontrolling interest, gain on the sale of held to maturity and available for sale securities, amortization of intangibles, goodwill and certain items deemed by S&P Global to be nonrecurring, including but not limited to, as applicable, net gains on disposition of premises and equipment, FDIC special assessments and CEO retirement costs, each of which are calculated on an after-tax basis. Core ROATCE is calculated as an average for each of the three calendar years of the performance period for the Company and all comparator banks in the KRX Index regardless of each entity’s fiscal year end. Total Shareholder Return is calculated based on 20-trading day average periods prior to the beginning and end of the performance period and assumes any dividends in the beginning average and performance period are reinvested as of the payment date.

  82. 2025 Long-Term Incentive Plan

    | 61 | First Interstate BancSystem, Inc. |

  83. 2025 Long-Term Incentives Granted

    2025 Long-Term Incentives Granted The target LTI opportunity for each NEO is expressed as a percentage of base salary. The Compensation Committee annually reviews LTI target opportunities as part of its assessment of overall target total direct compensation, considering peer market data prepared by Pearl Meyer. As described above under “2025 Compensation Highlights—Compensation Opportunities,” in late 2023, the Compensation Committee undertook a two-year effort to better align non-CEO NEO target total direct compensation with competitive market practices. In 2024, base salaries for non-CEO NEOs remained unchanged (with the exception of an increase approved in August 2024 for Ms. Robbins to reflect additional responsibilities added to her role as Chief Operations Officer), while adjustments to LTI target opportunities were used to begin addressing identified market gaps. In the fall of 2024, the Compensation Committee reassessed target compensation, following an updated market analysis provided by Pearl Meyer and, in January 2025, reduced target LTI opportunities for the non-CEO NEOs, as a percentage of base salary by 20%, back to pre-2024 levels. Mr. Reuter’s target opportunity remained unchanged. The table below reflects the 2025 LTI Plan award target values and corresponding amounts approved by the Compensation Committee for the non-CEO NEOs and by the Board for our CEO.

  84. 2025 Long-Term Incentives Granted

    | | | Target Award | | PRSUs/RSUs Awarded | | | Officer | Base Salary at Grant Date ($) | Target (%) | Target LTI ($) | PRSUs at Target (#)(1) | RSUs (#)(1) | | James A. Reuter | 1,000,000 | 250 | 2,500,000 | 51,992 | 34,663 | | David P. Della Camera(2) | 280,000 | 40 | 112,000 | 3,534 | 2,358 | | Kristina R. Robbins | 460,000 | 70 | 322,000 | 6,696 | 4,465 | | Kirk D. Jensen | 453,643 | 70 | 317,550 | 6,602 | 4,404 | | Lori A. Meyer | 330,000 | 70 | 231,000 | 4,802 | 3,204 | | Marcy D. Mutch(3) | 566,951 | 100 | 566,951 | 11,790 | 7,861 | | Lorrie F. Asker | 484,000 | 100 | 484,000 | 10,064 | 6,712 |

  85. 2025 Long-Term Incentives Granted

    (1) The number of PRSUs and RSUs granted were calculated as 60%, and 40% respectively, of the executive’s approved LTI award based on the closing price of the underlying common stock as quoted on NASDAQ Stock Market for the last market trading day prior to the March 15 grant date of $28.85, rounded down to the nearest whole share. (2) At the time of the 2025 LTI grant, Mr. Della Camera was serving as Deputy CFO and his target LTI opportunity was 40% of base salary ($280,000). In recognition of his individual performance, management approved an above-target 2025 LTI Plan award for Mr. Della Camera with an approved award value of $170,000 upon which the number of PRSUs and RSUs shown in the table was determined. (3) At the time of the 2025 LTI grant, Ms. Mutch was over the age of 65 and retirement eligible under the terms of the award agreements. Accordingly: (i) her 2025 RSUs vested in full immediately upon grant, and (ii) she became entitled to receive her 2025 PRSUs following the end of the originally scheduled three-year performance period, with vesting based on achievement of specified performance conditions as outlined in the award agreement, in each case subject to certain forfeiture events. Ms. Mutch’s employment ended on December 31, 2025. Settlement and delivery of shares with respect to her vested 2025 RSUs will not occur until June 30, 2026 (or the date of her death, if earlier), in accordance with the six- month delay required under Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), for specified employees. For additional information regarding long-term incentives granted to our NEOs in 2025, see the information provided under the caption “Grants of Plan-Based Awards”. Grant date fair value calculations for the respective awards can be found within the footnotes provided under the Summary Compensation Table included in this proxy statement.

  86. 2023 Long-Term Incentive Performance Results

    2023 Long-Term Incentive Performance Results PRSUs granted in 2023 under the 2023 LTI Plan were subject to a three-year performance period from January 1, 2023 through December 31, 2025 and were based equally on relative Adjusted ROAE and Total Shareholder Return performance against companies included in the KRX Index. Neither metric achieved threshold performance, and as a result, none of the 2023 PRSUs vested.

  87. 2023 Long-Term Incentive Performance Results

    | 62 | First Interstate BancSystem, Inc. |

  88. 2023 Long-Term Incentive Performance Results

    For purposes of the 2023 PRSUs, Adjusted ROAE was calculated as Adjusted Net Income divided by average common shareholders’ equity. Adjusted Net Income, for purposes of this calculation, generally means net income before income tax, minus non-recurring revenue items, plus non-recurring expense items, with non-recurring items being defined by S&P Global (or its successor), including, as applicable, net gains on disposition of premises and equipment, FDIC special assessments and CEO retirement costs. Adjusted ROAE was calculated as an average of the respective measures for each of the three calendar years of the performance period for the Company and all comparator banks, regardless of each entity’s fiscal year end. Total Shareholder Return was calculated, for purposes of the 2023 PRSUs, using a closing price average of the 20 trading days immediately prior to the performance period and the last 20 trading days of the performance period. Relative performance results for Total Shareholder Return and Adjusted ROAE were calculated separately, with total shares vested and additional shares issued, if any, based on the sum of the results for the two metrics weighted equally. The performance results were as follows:

  89. 2023 Long-Term Incentive Performance Results

    | Performance Metric | Goal Weight | Threshold Performance | Target Performance | Maximum Performance | Performance Result | Vesting % | | Adjusted ROAE | 50% | 35th Percentile | 50th Percentile | 90th Percentile | 20th Percentile | 0% | | Total Shareholder Return | 50% | 35th Percentile | 50th Percentile | 90th Percentile | 28th Percentile | 0% | | 2023 LTI Performance Results | | | | | | 0% |

  90. 2023 Long-Term Incentive Performance Results

    The following chart shows the vesting results applied to the 2023 PRSUs for the NEOs who were impacted:

  91. 2023 Long-Term Incentive Performance Results

    | Officer | 2023 PRSUs Granted at Target (#) | 2023 PRSUs Vested (#) | | David P. Della Camera | 1,732 | — | | Kristina R. Robbins | 4,729 | — | | Kirk D. Jensen | 5,556 | — | | Lori A. Meyer | 1,154 | — | | Marcy D. Mutch | 10,393 | — | | Lorrie F. Asker | 3,849 | — |

  92. Policies and Practices for Granting Certain Equity Awards

    Policies and Practices for Granting Certain Equity Awards Equity awards are generally granted to our NEOs on March 15th of the applicable fiscal year. In certain circumstances, including the hiring or promotion of an officer, the Compensation Committee may approve grants to be effective at other times. The Company does not currently grant awards of stock options, stock appreciation rights, or similar option-like awards as part of its compensation program. The Company does not time the disclosure of material non-public information, or the granting of equity awards, for the purpose of impacting the value of executive compensation.

  93. Severance and Change-in-Control Benefits

    Severance and Change-in-Control Benefits We provide severance pay and other benefits to executive officers, including the NEOs, who have their employment terminated, including through involuntary termination by us without cause and, in some cases, voluntary termination of the executive for good reason. These arrangements provide security of transition income and benefit replacements that allow such executives to focus on our prospective business priorities that create value for shareholders. We believe the level of severance and benefits provided by these arrangements is consistent with the practices of our peers and are necessary to attract and retain key employees. Potential payments and benefits available under these arrangements are discussed further in this proxy statement under the caption “Potential Payments upon Certain Termination Events”.

  94. Risk Assessment of Compensation Programs

    | ☑ | Use of multiple metrics in short and long-term incentive plans for executive officers; | | ☑ | Application of caps on incentives; | | ☑ | Providing time-based RSUs that vest ratably over three years and PRSUs that cliff vest after a three-year performance period; | | ☑ | Emphasizing long-term and performance-based compensation; | | ☑ | Instituting formal clawback policies applicable to both cash and equity performance-based compensation; and | | ☑ | Aligning interests of our executive officers with the long-term interests of our shareholders through equity ownership guidelines. |

  95. 2025 Summary Compensation Table

    2025 Summary Compensation Table The table below summarizes the total compensation paid or earned by each of the NEOs for 2025, 2024, and 2023, as required by applicable rules of the SEC.

  96. 2025 Summary Compensation Table

    | Name and Position | Year | Salary ($) | Bonus ($) | Stock Awards (1)(2)(3) ($) | Non-Equity Incentive Plan Compensation (4)($) | Change in Pension Value and Non-qualified Deferred Compensation Earnings (5)($) | All Other Compensation (6)($) | Total ($) | | James A. Reuter | 2025 | 1,000,000 | — | 2,534,832 | 1,044,000 | — | 36,177 | 4,615,009 | | President & Chief | 2024 | 138,462 | — | 2,117,821 | 200,000 | — | 84,523 | 2,540,806 | | Executive Officer | — | — | — | — | — | — | — | — | | David P. Della Camera(7) | 2025 | 403,539 | — | 172,352 | 304,500 | — | 22,066 | 902,457 | | Chief Financial Officer, | — | — | — | — | — | — | — | — | | EVP | — | — | — | — | — | — | — | — | | Kristina R. Robbins | 2025 | 448,462 | — | 326,481 | 280,140 | — | 33,381 | 1,088,464 | | Chief Operations Officer, | 2024 | 366,077 | — | 310,841 | 280,000 | — | 36,333 | 993,251 | | EVP | 2023 | 347,000 | — | 207,518 | 42,120 | — | 34,395 | 631,033 | | Kirk D. Jensen | 2025 | 445,712 | — | 321,946 | 276,269 | — | 49,837 | 1,093,764 | | General Counsel, EVP | 2024 | 412,402 | — | 365,229 | 288,682 | — | 44,415 | 1,110,728 | | | 2023 | 407,703 | — | 251,430 | 49,488 | — | 33,292 | 741,912 | | Lori A. Meyer | 2025 | 324,231 | — | 234,190 | 200,970 | — | 23,862 | 783,253 | | Chief Information Officer, | 2024 | — | — | — | — | — | — | — | | EVP | 2023 | — | — | — | — | — | — | — | | Marcy D. Mutch(8) | 2025 | 234,672 | — | 574,831 | 337,052 | — | 397,719 | 1,544,274 | | Former Chief Financial Officer, | 2024 | 539,954 | — | 637,610 | 431,963 | — | 47,985 | 1,657,512 | | EVP | 2023 | 533,801 | — | 482,881 | 75,594 | — | 37,480 | 1,129,756 | | Lorrie F. Asker(9) | 2025 | 438,308 | — | 490,730 | 336,864 | — | 82,469 | 1,348,371 | | Former Co-Chief Banking Officer, | 2024 | 440,000 | — | 519,579 | 352,000 | — | 40,979 | 1,352,558 | | EVP | 2023 | 377,885 | — | 268,317 | 61,600 | — | 22,690 | 730,492 |

  97. 2025 Summary Compensation Table

    (1) The amounts in the “Stock Awards” column reflect the aggregate grant date fair value of equity awards granted determined in accordance with FASB ASC Topic 718. The grant date fair value of the time-based RSUs and time-based RSAs utilized the closing price of a share of our common stock on the trading day immediately prior to the grant date in each year as follows: for 2025, $28.85 for RSUs granted under the 2025 LTI Plan; for 2024, $25.02 for RSUs granted under the 2024 LTI Plan and $30.80 for Mr. Reuter’s RSUs granted upon his start date as President and CEO; and for 2023, $24.04 for RSUs granted under the 2023 LTI Plan, $31.17 for a one-time special grant of RSAs, and $36.45 for Ms. Asker’s RSA award upon appointment as the Chief Banking Officer. (2) The value for the performance-based awards included in the stock awards aggregate total assume target level performance. As the performance-based awards are based on separate measurements of the Company’s financial performance, the portion of the PRSU awards attributed to Core ROATCE for 2025 PRSUs, Core ROAE for 2024 PRSUs, and Adjusted ROAE for 2023 PRSUs have a grant date fair value of $28.85, $25.02, and $24.04 per share, respectively. For the PRSU awards with performance vesting related to Total Shareholder Return in 2025, 2024, and 2023, the grant date fair values were determined using a Monte Carlo valuation method. The key assumptions used in the valuation were: (a) volatility; (b) correlations; and (c) the risk-free rate of return. Based on these assumptions, the awards were valued at $30.19, $23.69, and $14.24 per share, respectively. For Mr. Reuter’s PRSU award granted on his start date of November 1, 2024, the Monte Carlo value was $36.85 per share. Grant date fair values assuming maximum performance levels are achieved for the 2025 PRSU awards would be $3,069,607 for Mr. Reuter, $208,647 for Mr. Della Camera, $395,332 for Ms. Robbins, $389,782 for Mr. Jensen, $283,510 for Ms. Meyer, $696,082 for Ms. Mutch, and $594,178 for Ms. Asker.

  98. 2025 Summary Compensation Table

    | 67 | First Interstate BancSystem, Inc. |

  99. 2025 Summary Compensation Table

    (3) The stock awards for each NEO consists of the following for the applicable periods during which they qualified as a NEO for the Company:

  100. 2025 Summary Compensation Table

    | Name | Year | Time-Based Restricted Equity Awards (#) | Performance-Based Restricted Equity Awards (#)(a) | | James A. Reuter | 2025 | 34,663 | 51,992 | | | 2024 | 25,974 | 38,960 | | | 2023 | — | — | | David P. Della Camera | 2025 | 2,358 | 3,534 | | | 2024 | — | — | | | 2023 | — | — | | Kristina R. Robbins | 2025 | 4,465 | 6,696 | | | 2024 | 5,051 | 7,574 | | | 2023 | 4,475 | 4,729 | | Kirk D. Jensen | 2025 | 4,404 | 6,602 | | | 2024 | 5,934 | 8,900 | | | 2023 | 5,502 | 5,556 | | Lori A. Meyer | 2025 | 3,204 | 4,802 | | | 2024 | — | — | | | 2023 | — | — | | Marcy D. Mutch | 2025 | 7,861 | 11,790 | | | 2024 | 10,359 | 15,538 | | | 2023 | 10,695 | 10,393 | | Lorrie F. Asker | 2025 | 6,712 | 10,064 | | | 2024 | 8,443 | 12,660 | | | 2023 | 6,367 | 3,849 |

  101. 2025 Summary Compensation Table

    (a) The number of performance-based awards assumes target level performance. (4) The values shown for 2025 are the final payouts under the 2025 STI Plan. For more information regarding our 2025 STI Plan, see “Short-Term Incentives” in CD&A. (5) The Company does not provide above-market or preferential earnings on deferred compensation. See the information provided under “2025 Non-Qualified Deferred Compensation Table” included in this proxy statement for information about deferred compensation.

  102. 2025 Summary Compensation Table

    | 68 | First Interstate BancSystem, Inc. |

  103. 2025 Summary Compensation Table

    (6) The amount of “All Other Compensation” consists of the following for each NEO:

  104. 2025 Summary Compensation Table

    | Name | 401K Match ($) | Personal Use of Company Vehicle/ Aircraft ($) | Dividends On Equity Awards(a) ($) | Social Club Dues ($) | Relocation Expenses ($) | Matching Charitable Contributions(b) ($) | Other (c)(d) ($) | Total ($) | | James A. Reuter | 20,769 | 12,018 | — | — | — | 3,390 | — | 36,177 | | David P. Della Camera | 13,499 | — | 7,506 | — | — | 1,000 | 61 | 22,066 | | Kristina R. Robbins | 15,231 | — | 8,308 | 9,842 | — | — | — | 33,381 | | Kirk D. Jensen | 21,000 | — | 8,995 | 9,842 | — | 10,000 | — | 49,837 | | Lori A. Meyer | 19,454 | — | 3,908 | — | — | 500 | — | 23,862 | | Marcy D. Mutch | 21,000 | — | 16,585 | 3,180 | — | 10,000 | 346,954 | 397,719 | | Lorrie F. Asker | 21,000 | — | 10,522 | 11,766 | — | 1,950 | 37,231 | 82,469 |

  105. 2025 Summary Compensation Table

    (a) These amounts reflect cash dividend equivalent payments made to each NEO in 2025 on time-based RSUs and RSAs. (b) The amounts shown in this column reflect matching contributions made under First Interstate BancSystem Foundation’s Matching Gift Program. (c) The amount reflects company matching contributions on base salary deferrals to Mr. Della Camera made under the First Interstate BancSystem Deferred Compensation Plan. (d) For Ms. Mutch and Ms. Asker, the amounts reflect compensation received in 2025 while employed as Executive Advisor. For Ms. Mutch the amount also includes $19,867 in attorneys’ fees reimbursed by the Company in connection with the review and finalization of the Mutch Transition Agreement. (7) Mr. Della Camera, who previously served as our Deputy CFO, was appointed as EVP and CFO, effective June 1, 2025. See “NEO Agreements— Other Continuing NEOs” for additional information regarding Mr. Della Camera’s employment information. (8) Ms. Mutch retired as EVP and CFO, effective May 31, 2025. From June 1, 2025 to December 31, 2025, Ms. Mutch remained employed by the Company as an Executive Advisor pursuant to the terms of the Mutch Transition Agreement. See “NEO Agreements— Transition Agreement with Marcy D. Mutch” herein for additional information regarding the Mutch Transition Agreement and related compensation payable to Ms. Mutch. (9) Effective November 14, 2025, Ms. Asker transitioned from Co-Chief Banking Officer to Executive Advisor pursuant to the terms of the Asker Transition Agreement. See “NEO Agreements— Transition Agreement with Lorrie F. Asker” herein for additional information regarding the Asker Transition Agreement and related compensation payable to Ms. Asker.

  106. Grants of Plan-Based Awards

    Grants of Plan-Based Awards

  107. Grants of Plan-Based Awards

    | | | | | | | | | | | All Other Awards | | | | | | | Estimated Possible Payouts Under Non-Equity Incentive Plan Awards (1) | | | Estimated Future Payouts Under Equity Incentive Plan Awards(2) | | | Stock Awards: Number of Shares or Units(3) (#) | Grant Date Fair Value of Stock Awards(4) ($) | | Name | Award | Grant Date | Approval Date | Threshold ($) | Target ($) | Max ($) | Threshold (#) | Target (#) | Max (#) | | | | James A. Reuter | STI | | | 600,000 | 1,200,000 | 2,400,000 | — | — | — | | | | | 2025 LTI | 3/15/2025 | 2/26/2025 | — | — | — | — | — | — | 34,663 | 1,000,028 | | | 2025 LTI | 3/15/2025 | 2/26/2025 | | — | — | 25,996 | 51,992 | 103,984 | — | 1,534,804 | | David P. Della Camera | STI | | | 175,000 | 350,000 | 700,000 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 2,358 | 68,028 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 1,767 | 3,534 | 7,068 | — | 104,324 | | Kristina R. Robbins | STI | | | 161,000 | 322,000 | 644,000 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 4,465 | 128,815 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 3,348 | 6,696 | 13,392 | — | 197,666 | | Kirk D. Jensen | STI | | | 158,775 | 317,550 | 635,100 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 4,404 | 127,055 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 3,301 | 6,602 | 13,204 | — | 194,891 | | Lori A. Meyer | STI | | | 115,500 | 231,000 | 462,000 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 3,204 | 92,435 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 2,401 | 4,802 | 9,604 | — | 141,755 | | Marcy D. Mutch(5) | STI | | | 193,708 | 387,417 | 774,833 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 7,861 | 226,790 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 5,895 | 11,790 | 23,580 | — | 348,041 | | Lorrie F. Asker | STI | | | 193,600 | 387,200 | 774,400 | — | — | — | — | — | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | — | — | — | 6,712 | 193,641 | | | 2025 LTI | 3/15/2025 | 1/22/2025 | — | — | — | 5,032 | 10,064 | 20,128 | — | 297,089 |

  108. Grants of Plan-Based Awards

    (1) This represents the range of possible payouts for the 2025 STI Plan under our annual STI Plan as discussed under the heading “2025 STI Plan” in CD&A. (2) This represents the range of possible payouts for the PRSU awards granted under our 2025 LTI Plan. Vesting of any earned PRSUs generally occurs, depending on achievement in the three-year performance period ending on December 31, 2027, on March 15, 2028. Additional details of our PRSU awards are discussed under the heading “2025 Long-Term Incentives Granted” in CD&A. (3) This represents the time-based RSU awards granted under our 2025 LTI Plan, which have a three-year graded vesting period with 1/3 of the award vesting each year. Additional details of these RSUs are described under the heading “2025 Long-Term Incentives Granted” in CD&A. (4) The grant date fair value listed in the chart above is reflective of FASB ASC Topic 718. See footnotes 1 and 2 of the Summary Compensation Table for further details. (5) At the time of the 2025 LTI grant, Ms. Mutch was over the age of 65 and retirement eligible under the terms of the award agreements. Accordingly: (i) her 2025 RSUs vested in full immediately upon grant, and (ii) she became entitled to receive her 2025 PRSUs following the end of the originally scheduled three-year performance period, with vesting based on achievement of specified performance conditions as outlined in the award agreement, in each case subject to certain forfeiture events.

  109. Grants of Plan-Based Awards

    | 71 | First Interstate BancSystem, Inc. |

  110. Outstanding Equity Awards as of December 31, 2025

    Outstanding Equity Awards as of December 31, 2025

  111. Outstanding Equity Awards as of December 31, 2025

    | | | Stock Awards | | | | | | | Time-based | | Performance-based | | | Name | Award | Number of Shares or Units of Stock That Have Not Vested (#)(1) | Market Value of Shares or Units of Stock That Have Not Vested ($)(3) | Equity incentive Plan awards: Number of Unearned Shares, Units, or Other Rights That Have Not Vested (#)(2) | Equity incentive plan awards: Market Value of Payout Value of Unearned Shares, Units, or Other Rights That Have Not Vested ($)(3) | | James A. Reuter | 2025 LTI(4) | 34,663 | 1,199,340 | 103,984 | 3,597,846 | | | 2024 Sign-On Grant(5) | 25,974 | 898,700 | 38,960 | 1,348,016 | | David P. Della Camera | 2025 LTI(4) | 2,358 | 81,587 | 7,068 | 244,553 | | | 2024 LTI(6) | 6,556 | 226,838 | 2,158 | 74,667 | | | 2024 RSU Ad-Hoc(7) | 9,221 | 319,047 | — | — | | | 2023 LTI(8) | 385 | 13,321 | 866 | 29,964 | | Kristina R. Robbins | 2025 LTI(4) | 4,465 | 154,489 | 13,392 | 463,363 | | | 2024 LTI(6) | 3,368 | 116,533 | 7,574 | 262,060 | | | 2023 LTI(8) | 1,051 | 36,365 | 2,365 | 81,829 | | Kirk D. Jensen | 2025 LTI(4) | 4,404 | 152,378 | 13,204 | 456,858 | | | 2024 LTI(6) | 3,956 | 136,878 | 8,900 | 307,940 | | | 2023 LTI(8) | 1,235 | 42,731 | 2,778 | 96,119 | | Lori A. Meyer | 2025 LTI(4) | 3,204 | 110,858 | 9,604 | 332,298 | | | 2024 LTI(6) | 2,878 | 99,579 | 6,474 | 224,000 | | | 2023 LTI(8) | 257 | 8,892 | 577 | 19,964 | | Marcy D. Mutch | 2025 LTI(4) | — | — | 23,580 | 815,868 | | | 2024 LTI(6) | — | — | 15,538 | 537,615 | | | 2023 LTI(8) | — | — | — | — | | Lorrie F. Asker | 2025 LTI(4) | 6,712 | 232,235 | 20,128 | 696,429 | | | 2024 LTI(6) | 5,629 | 194,763 | 12,660 | 438,036 | | | 2023 LTI(8) | 856 | 29,618 | 1,925 | 66,605 | | | 2023 RSA Ad-Hoc(9) | 915 | 31,659 | — | — |

  112. Outstanding Equity Awards as of December 31, 2025

    (1) Represents unvested time-based RSAs/RSUs, which vest contingent on continued employment. In 2024, Ms. Mutch attained the age of 65 and became retirement eligible under the terms of the respective award agreements and, as a result, her 2023 and 2024 RSUs vested in full in 2024. In addition, her 2025 RSUs vested in full immediately upon grant, as further described below (see “Stock Awards Vested During 2025”). Ms. Mutch’s employment ended on December 31, 2025. Settlement and delivery of shares with respect to her vested RSUs will not occur until June 30, 2026 (or the date of her death, if earlier), in accordance with the six-month delay required under Section 409A of the Code for specified employees. (2) Represents the number of PRSUs outstanding as of December 31, 2025, reported in accordance with applicable SEC rules. For PRSUs granted in 2023, reflects payouts at threshold level. For Mr. Reuter’s Sign-On Grant and the PRSUs granted in 2024, reflects payout at target level. For PRSUs granted in 2025, reflects payout at maximum level. The actual number of shares to vest will be based upon achievement of specified performance conditions and continued employment. For Ms. Mutch, upon becoming retirement eligible under the terms of the respective performance-based award agreements: (i) she became entitled to receive her 2024 and 2025 PRSUs following the end of the originally scheduled three-year performance period, with vesting based on achievement of specified performance conditions as outlined in the respective award agreements, subject to certain forfeiture events prior to delivery, and (ii) her 2023 PRSUs became eligible to vest following the end of the three-year performance period ended on December 31, 2025, although none actually vested on December 31, 2025 because threshold performance was not attained. (3) Market value is based on closing price of the common stock as of December 31, 2025 of $34.60 per share. (4) Represents the outstanding LTI award granted on March 15, 2025. The PRSUs are subject to a three-year performance period ending December 31, 2027 with a vest date of March 15, 2028. The RSUs are scheduled to vest equally over three years on March 15, 2026, 2027, and 2028.

  113. Outstanding Equity Awards as of December 31, 2025

    | 72 | First Interstate BancSystem, Inc. |

  114. Outstanding Equity Awards as of December 31, 2025

    (5) Represents the award granted to Mr. Reuter in November 2024 on his start date as President and CEO. The RSUs are generally scheduled to vest on November 1, 2029. The PRSUs are subject to a five-year performance period ending December 31, 2029 with a vest date of March 15, 2030. Further details are provided below under the heading “NEO Agreements— James A. Reuter”. (6) Represents the outstanding LTI award granted on March 15, 2024. The PRSUs are subject to a three-year performance period ending December 31, 2026 with a vest date of March 15, 2027. The RSUs are scheduled to vest in equal parts on March 15, 2026 and 2027. (7) Represents the outstanding RSUs of the award granted to Mr. Della Camera on May 25, 2024 upon being appointed as Deputy CFO. The RSUs will vest on May 25, 2027. (8) Represents the outstanding LTI award granted on May 24, 2023. The RSUs vested March 15, 2026. The PRSUs are subject to a three-year performance period ending December 31, 2025 with a vest date of March 15, 2026. As described in CD&A under the heading "2023 Long-Term Incentive Performance Results", the 2023 PRSUs did not achieve threshold performance, and as a result, none of the PRSUs vested on March 15, 2026. (9) Represents the outstanding RSAs of the award granted to Ms. Asker on February 9, 2023 upon being appointed as the interim Chief Banking Officer. These RSAs vested on February 9, 2026.

  115. Non-Qualified Deferred Compensation

    Non-Qualified Deferred Compensation The Company has a non-qualified deferred compensation plan (the “Deferred Compensation Plan”) established for the benefit of a select group of management and highly compensated employees, including NEOs and active members of the Board. Under the terms of our Deferred Compensation Plan, eligible employees, as determined by our Board or Compensation Committee, may defer a portion of base salary, short-term incentive bonuses and other remuneration earned, subject to minimum and maximum limitations set forth under the plan. Deferral elections generally are made by eligible employees during the last quarter of each year for compensation to be earned in the following year. Employees can make an election to receive their benefit upon separation of employment in a lump sum, or in monthly or annual installments over 2 to 15 years; or an election to receive their benefit upon a chosen date that is 1 or more years following the year of deferral, in the form of a lump sum or in annual installments over 2 to 5 years. Eligible employees are permitted to change the time and/or form of a scheduled distribution in accordance with procedures established by the plan administrator, provided that such election to change the time or form of a payment must be made at least 12 months prior to the date on which the payment is scheduled to be made, the payment must be deferred for at least five years from the date the payment would have otherwise been made and the election cannot take effect until at least 12 months after the date on which it is made. Distribution elections and subsequent distribution elections are

  116. Non-Qualified Deferred Compensation

    | 73 | First Interstate BancSystem, Inc. |

  117. Non-Qualified Deferred Compensation

    required to be made in accordance with Section 409A of the Code. We make discretionary matching contributions to the Deferred Compensation Plan with respect to each employee participant who has elected to defer base salary compensation. Other Company contributions on behalf of a participant may be made to a participant at the discretion of our Board. The deferral account of each participant is credited with investment earnings or losses based upon the performance of the underlying hypothetical investments suggested by the participant from among alternatives selected by the plan administrator. The following table shows the contributions, earnings, and aggregate balance of total deferrals for each of our NEOs as of December 31, 2025.

  118. Non-Qualified Deferred Compensation

    | Name | Plan | Executive Contributions in Last Fiscal Year ($)(1) | Registrant Contributions in Last Fiscal Year ($)(2) | Aggregate Earnings in Last Fiscal Year ($)(3) | Aggregate Withdrawals/ Distributions ($)(4) | Aggregate Balance at Last Fiscal Year End ($) | | (a) | | (b) | (c) | (d) | (e) | (f) | | James A. Reuter | — | — | — | — | — | — | | David P. Della Camera | DCP | 39,036 | 61 | 5,650 | — | 86,117 | | Kristina R. Robbins | — | — | — | — | — | — | | Kirk D. Jensen | DCP | — | — | 54 | — | 1,342 | | Lori A. Meyer | DCP | — | — | 47 | — | 392 | | Marcy D. Mutch | DCP | — | — | 94,418 | — | 733,154 | | | 2023 Plan - RSUs(5) | 226,790 | — | 76,759 | 182,025 | 635,526 | | Lorrie F. Asker | DCP | — | — | 9,366 | — | 64,769 |

  119. Non-Qualified Deferred Compensation

    (1) The amounts in column (b) represent: (i) with respect to the Deferred Compensation Plan, or DCP, salary and/or short-term incentives that were deferred into the DCP in 2025, which amounts are also included in the applicable column of the 2025 Summary Compensation Table above; and (ii) with respect to the 2023 Plan, the grant date fair value of Ms. Mutch’s 2025 RSU award, which vested in full immediately upon grant because Ms. Mutch was retirement eligible under the terms of the award agreement. This amount is also included in the “Stock Awards” column of the 2025 Summary Compensation Table above. See footnote 1 to the 2025 Summary Compensation Table for additional details. (2) The amounts in column (c) represent the Company’s contributions made to the NEOs’ accounts under the Deferred Compensation Plan in 2025, which, in the case of Mr. Della Camera, represents a Company matching contribution that is also included in the “All Other Compensation” column of the 2025 Summary Compensation Table above. (3) With respect to the DCP, the amounts in this column reflect earnings tied to changes in the value of publicly traded investment funds. With respect to the 2023 Plan, the amounts in this column represent (i) for the 2023 and 2024 RSUs that have not been distributed as of December 31, 2025, the change in the closing price of the Company’s common stock during 2025; (ii) for the 2023 and 2024 RSUs distributed on March 17, 2025, the change in the closing price of the Company’s common stock from December 31, 2024 to the distribution date; (iii) for the 2025 RSUs, the change in the closing price of the Company’s common stock from the grant date to December 31, 2025; and (iv) the amount of dividend equivalents credited in 2025 with respect to the 2023, 2024 and 2025 RSUs (which are paid to the recipient at the time the underlying shares are distributed). None of the amounts reported in this column are reported in the 2025 Summary Compensation Table because the Company does not pay guaranteed, above-market or preferential earnings on deferred compensation. (4) The amounts in column (e) represent the distributions made on March 17, 2025 to Ms. Mutch with respect to 2,310 RSUs (initially granted as part of the 2023 LTI Plan) and 3,453 RSUs (initially granted as part of the 2024 LTI Plan), each of which vested in 2024 upon Ms. Mutch reaching age 65 and becoming retirement eligible. (5) The 2023, 2024 and 2025 RSUs are reflected in this table under applicable SEC rules because, and to the extent that, the underlying shares of common stock have not yet been distributed as of December 31, 2025. The shares underlying Ms. Mutch’s deferred RSUs will not be distributed to Ms. Mutch until six months following her December 31, 2025 separation from service (or the date of her death, if earlier), pursuant to Section 409A of the Code and the terms of the applicable award agreements.

  120. Non-Qualified Deferred Compensation

    | 74 | First Interstate BancSystem, Inc. |

  121. CEO Pay Ratio

    CEO Pay Ratio As required by Section 953(b) of the Dodd-Frank Wall Street Reform and Consumer Protection Act, we are providing the following information about the relationship of the annual total compensation of our CEO and the median annual total compensation of all other employees for 2025.

  122. CEO Pay Ratio

    | Median Employee (other than CEO) Total Annual Compensation | CEO Total Annual Compensation | Ratio of CEO to Median Employee (other than CEO) Total Annual Compensation | | $59,825 | $4,615,009 | 77 to 1 |

  123. Pay Versus Performance

    Pay Versus Performance In accordance with rules adopted by the SEC pursuant to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, we provide the following disclosure regarding executive “compensation actually paid” (“CAP”, as calculated in accordance with applicable SEC rules), and certain Company performance measures for the fiscal years listed below. For information regarding the Company’s pay-for-performance philosophy and how the Company aligns executive pay with performance, refer to our CD&A.

  124. Pay Versus Performance

    | 75 | First Interstate BancSystem, Inc. |

  125. Pay Versus Performance Table

    Pay Versus Performance Table The following table provides the information required for our NEOs for each of the fiscal years ended December 31, 2025, December 31, 2024, December 31, 2023, December 31, 2022, and December 31, 2021, along with the financial information required to be disclosed for each fiscal year:

  126. Pay Versus Performance Table

    | Year | Kevin P. Riley | | James A. Reuter | | Average Summary Comp- ensation Table Total for non- PEO NEOs ($)(2) | Average Summary Comp- ensation Actually Paid to non-PEO NEOs ($)(2)(3) | Value of Initial Fixed $100 Investment Based On: | | Net Income (in $M) ($) | Core ROATCE (%)(4) | | | Summary Comp- ensation Table Total for PEO ($)(1) | Comp- ensation Actually Paid to PEO ($)(1)(3) | Summary Comp- ensation Table Total for PEO ($)(1) | Comp- ensation Actually Paid to PEO ($)(1)(3) | | | Company Total Shareholder Return ($) | KBW Regional Banking Index Total Shareholder Return ($) | | | | (a) | (b) | (c) | (b) | (c) | (d) | (e) | (f) | (g) | (h) | (i) | | 2025 | — | — | 4,615,009 | 4,684,633 | 1,126,764 | 1,155,714 | 112.10 | 152.72 | 302.1 | 12.16 | | 2024 | 4,870,569 | 4,324,053 | 2,540,806 | 2,689,115 | 1,278,512 | 1,234,476 | 98.91 | 143.40 | 226.0 | 11.54 | | 2023 | 3,384,896 | 1,951,042 | — | — | 835,999 | 550,266 | 87.57 | 126.67 | 257.5 | 15.23 | | 2022 | 4,617,084 | 4,215,324 | — | — | 1,482,037 | 1,343,374 | 102.77 | 127.18 | 202.2 | 16.22 | | 2021 | 3,201,243 | 2,342,207 | — | — | 928,135 | 733,189 | 103.59 | 136.65 | 192.1 | 16.35 |

  127. Pay Versus Performance Table

    (1) James A. Reuter served as our President and CEO for all of 2025. For the year ended December 31, 2024, Kevin P. Riley served as our PEO until November 1, 2024 when James A. Reuter became our President and CEO. Kevin P. Riley was the PEO for each of the years ended December 31, 2023, 2022, and 2021. (2) For the year ended December 31, 2025, the non-PEO NEOs were David P. Della Camera, Kristina R. Robbins, Kirk D. Jensen, Lori A. Meyer, Marcy D. Mutch, and Lorrie F. Asker. For the year ended December 31, 2024, the non-PEO NEOs were Marcy D. Mutch, Lorrie F. Asker, Kirk D. Jensen, and Kristina R. Robbins. For the year ended December 31, 2023, the non-PEO NEOs were Marcy D. Mutch, Kirk D. Jensen, Lorrie F. Asker, Kristina R. Robbins, Ashley Hayslip, and Scott E. Erkonen. For the year ended December 31, 2022, the non-PEO NEOs were Marcy D. Mutch, Jodi Delahunt Hubbell, Kirk D. Jensen, Karlyn M. Knieriem, Scott E. Erkonen, and Russell A. Lee. For the year ended December 31, 2021, the non-PEO NEOs were Marcy D. Mutch, Jodi Delahunt Hubbell, Russell A. Lee, and Kirk D. Jensen. (3) Adjustments to total compensation in the Summary Compensation Table (“SCT”), reported in columns (b) and (d), to calculate CAP, reported in columns (c) and (e) for 2025, include:

  128. Pay Versus Performance Table

    | | PEO: James A. Reuter | Average Other NEOs | | | 2025 ($) | 2025 ($) | | Summary Compensation Total | 4,615,009 | 1,126,764 | | - Grant Date Fair Value of Stock Awards Granted in Fiscal Year | (2,534,832) | (353,422) | | + Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Awards Granted in Fiscal Year | 2,986,326 | 416,376 | | + Change in Fair Value of Outstanding and Unvested Stock Awards Granted in Prior Fiscal Years | (381,870) | (16,109) | | + Fair Value at Vesting of Stock Awards Granted in Fiscal Year That Vested During Fiscal Year | — | — | | + Change in Fair Value as of Vesting Date of Stock Awards Granted in Prior Fiscal Years For Which Applicable Vesting Conditions Were Satisfied During Fiscal Year | — | (17,895) | | - Fair Value as of Prior Fiscal Year-End of Stock Awards Granted in Prior Fiscal Years That Failed to Meet Applicable Vesting Conditions During Fiscal Year | — | | | + Value of Dividends or other Earnings Paid on Stock Awards not Otherwise Reflected in Fair Value or Total Compensation | — | — | | Compensation Actually Paid | 4,684,633 | 1,155,714 |

  129. Pay Versus Performance Table

    a.The methodologies used for determining the fair values shown in the table are materially consistent with those used to determine the fair values disclosed as of the grant date for each award. (4) For 2025, our Company Selected Measure is Core ROATCE, consistent with our LTI Plan. In prior years, we used Compensation Adjusted ROAE. For more details, see “2025 Long-Term Incentive Plan Design” and “2025 Long-Term Incentive Plan” in CD&A.

  130. Pay Versus Performance Table

    | 76 | First Interstate BancSystem, Inc. |

  131. Pay Versus Performance: Graphical Description

    Pay Versus Performance: Graphical Description The illustrations below provide graphical descriptions of the relationships between the following:

  132. Pay Versus Performance: Graphical Description

    | •CAP and the Company’s & Peer Group’s cumulative TSR; | | •CAP and the Company’s Net Income; and | | •CAP and the Company’s Core ROATCE |

  133. Pay Versus Performance: Graphical Description

    | 77 | First Interstate BancSystem, Inc. |

  134. Pay Versus Performance: Graphical Description

    | 78 | First Interstate BancSystem, Inc. |

  135. Potential Payments Upon Certain Termination Events

    Potential Payments Upon Certain Termination Events The disclosures below describe the payments to which the executives would have been entitled had they been terminated on December 31, 2025. Except as otherwise noted below, the cash severance and continued benefits described in this section are generally contingent upon (i) the applicable executive’s execution and non-revocation of a release of claims (to the extent required under the applicable agreement) and (ii) continued compliance with applicable post-termination restrictive covenants (including non-competition and non-solicitation restrictions) for the applicable restricted period (generally 12-18 months for the Other Continuing NEOs and 18-24 months for Mr. Reuter, depending on the circumstances of termination), as described under “NEO Agreements” above.

  136. Potential Payments Upon Termination or Change-in-Control Payments

    Potential Payments Upon Termination or Change-in-Control Payments

  137. as of 12/31/2025 - Mr. James A. Reuter

    | Executive Payments and Benefits upon Termination or Change in Control | Voluntary Termination | Involuntary Termination for Cause | Involuntary Termination Without Cause/ Termination for Good Reason | Change in Control With Termination for Good Reason or Without Cause | Death | Disability | | Compensation: | | | | | | | | Severance | $— | $— | $2,400,000(a) | $5,500,000(b) | $— | $— | | Pro-rata Bonus | — | — | — | 1,200,000(c) | — | — | | Long-term Incentives | | | | | | | | - Time-Restricted Awards (d) | — | — | 1,621,447 | 2,207,954 | 2,207,954 | 2,207,954 | | - Performance Awards (e) | — | — | 2,432,065 | 3,311,804 | 3,311,804 | 3,311,804 | | Benefits & Perquisites: | | | | | | | | Health Benefits (f) | — | — | 19,503 | 19,503 | — | — | | Total | $— | $— | $6,473,015 | $12,239,261 | $5,519,758 | $5,519,758 |

  138. Potential Payments Upon Termination or Change-in-Control Payments

    Potential Payments Upon Termination or Change-in-Control Payments

  139. as of 12/31/2025 - Mr. David P. Della Camera

    | Executive Payments and Benefits upon Termination or Change in Control | Voluntary Termination | Involuntary Termination for Cause | Involuntary Termination Without Cause/ Termination for Good Reason | Change in Control With Termination for Good Reason or Without Cause | Death | Disability | | Compensation: | | | | | | | | Severance | $— | $— | $620,000(a) | $1,700,000(b) | $— | $— | | Pro-rata Bonus | — | — | — | 350,000(c) | — | — | | Long-term Incentives | | | | | | | | - Time-Restricted Awards (d) | — | — | — | 693,499 | 693,499 | 693,499 | | - Performance Awards (e) | — | — | — | 277,094 | 277,094 | 277,094 | | Benefits & Perquisites: | | | | | | | | Survivor Income Benefits (f) | — | — | — | — | 150,000 | — | | Health Benefits (g) | — | — | 26,811 | 53,622 | — | — | | Total | $— | $— | $646,811 | $3,074,215 | $1,120,593 | $970,593 |

  140. Potential Payments Upon Termination or Change-in-Control Payments

    Potential Payments Upon Termination or Change-in-Control Payments

  141. as of 12/31/2025 - Ms. Kristina R. Robbins

    | Executive Payments and Benefits upon Termination or Change in Control | Voluntary Termination | Involuntary Termination for Cause | Involuntary Termination Without Cause/ Termination for Good Reason | Change in Control With Termination for Good Reason or Without Cause | Death | Disability | | Compensation: | | | | | | | | Severance | $— | $— | $667,373(a) | $1,564,000(b) | $— | $— | | Pro-rata Bonus | — | — | — | 322,000(c) | — | — | | Long-term Incentives | | | | | | | | - Time-Restricted Awards (d) | — | — | — | 329,703 | 329,703 | 329,703 | | - Performance Awards (e) | — | — | — | 713,952 | 713,952 | 713,952 | | Benefits & Perquisites: | | | | | | | | Survivor Income Benefits (f) | — | — | — | — | 150,000 | — | | Health Benefits (g) | — | — | 28,925 | 57,850 | — | — | | Total | $— | $— | $696,298 | $2,987,505 | $1,193,655 | $1,043,655 |

  142. Potential Payments Upon Termination or Change-in-Control Payments

    Potential Payments Upon Termination or Change-in-Control Payments

  143. as of 12/31/2025 - Mr. Kirk D. Jensen

    | Executive Payments and Benefits upon Termination or Change in Control | Voluntary Termination | Involuntary Termination for Cause | Involuntary Termination Without Cause/ Termination for Good Reason | Change in Control With Termination for Good Reason or Without Cause | Death | Disability | | Compensation: | | | | | | | | Severance | $— | $— | $692,378(a) | $1,542,386(b) | $— | $— | | Pro-rata Bonus | — | — | — | 317,550(c) | — | — | | Long-term Incentives | | | | | | | | - Time-Restricted Awards (d) | — | — | — | 357,016 | 357,016 | 357,016 | | - Performance Awards (e) | — | — | — | 793,310 | 793,310 | 793,310 | | Benefits & Perquisites: | | | | | | | | Survivor Income Benefits (f) | — | — | — | — | 150,000 | — | | Health Benefits (g) | — | — | 27,052 | 54,103 | — | — | | Total | $— | $— | $719,430 | $3,064,365 | $1,300,326 | $1,150,326 |

  144. Potential Payments Upon Termination or Change-in-Control Payments

    Potential Payments Upon Termination or Change-in-Control Payments

  145. as of 12/31/2025 - Ms. Lori A. Meyer

    | Executive Payments and Benefits upon Termination or Change in Control | Voluntary Termination | Involuntary Termination for Cause | Involuntary Termination Without Cause/ Termination for Good Reason | Change in Control With Termination for Good Reason or Without Cause | Death | Disability | | Compensation: | | | | | | | | Severance | $— | $— | $452,224(a) | $1,122,000(b) | $— | $— | | Pro-rata Bonus | — | — | — | 231,000(c) | — | — | | Long-term Incentives | | | | | | | | - Time-Restricted Awards (d) | — | — | — | 234,524 | 234,524 | 234,524 | | - Performance Awards (e) | — | — | — | 463,572 | 463,572 | 463,572 | | Benefits & Perquisites: | | | | | | | | Survivor Income Benefits (f) | — | — | — | — | 150,000 | — | | Health Benefits (g) | — | — | — | — | — | — | | Total | $— | $— | $452,224 | $2,051,096 | $848,096 | $698,096 |