NBT Bancorp Inc.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On September 21, 2026, the Board of Directors (the “Board”) of NBT Bancorp Inc. (“NBT”) increased the size of the Board to thirteen directors and appointed Kimberly A. Boynton to fill the newly created vacancy, effective October 1, 2026. Ms. Boynton, age 57, is a licensed real estate agent with Cushman & Wakefield | Pyramid Brokerage Company specializing in office and industrial real estate in upstate New York. Ms. Boynton previously served as President and Chief Executive Officer of Crouse Health, as well as Vice President of the Crouse Health Foundation, from January 2014 until March 2023. She began her career at Crouse in 1998 and served as Chief Financial Officer from 2003 until her appointment as Chief Executive Officer. Prior to joining Crouse Health, she worked in public accounting with Coopers & Lybrand in Syracuse, New York. Ms. Boynton has extensive experience serving on boards for business, nonprofit and community organizations, including serving as a director for a smaller bank holding company in Central New York. She has served on the Board of Trustees of SCR, Inc., a national defense contractor, since 2016 and is currently Vice Chairperson. She has also served on the Board of Directors of Byrne Dairy, Inc. since October 2023, AAA of Western and Central New York since 2005, AAA National since May 2024, NYSTEC (a nonprofit technology consulting organization) since 2024, The Century Club of Syracuse since January 2024, and Christian Brothers Academy since 2010. Ms. Boynton’s strong background in executive leadership in healthcare, financial management, board governance and commercial real estate will bring valuable perspective to the Board on the Central New York business community, the regional economy and the needs of the local communities NBT serves. The Board has determined that Ms. Boynton meets the standards of independence set forth by Nasdaq. Ms. Boynton is expected to serve on the Audit Committee, the Compensation and Benefits Committee and the Risk Management Committee of the Board. There are no transactions between Ms. Boynton or any member of her immediate family and NBT that would be reportable as a related party transaction under Item 404(a) of Regulation S-K. Ms. Boynton was not selected as a director because of any arrangement or understanding between Ms. Boynton or NBT and any other person and was not provided any compensation in connection with her appointment as a director. Ms. Boynton will be entitled to standard compensation as a director of NBT as disclosed in the proxy statement for NBT’s annual meeting of stockholders. She will receive a prorated annual grant of restricted stock units and prorated annual retainers for Board and applicable committee service.