First Business Financial Services, Inc.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On May 22, 2026 the Board of Directors (the “Board”) of First Business Financial Services, Inc. (the “Company”) increased the number of Directors constituting the entire Board from eight (8) to nine (9), and, in accordance with Section 3.10 of the Company’s Amended and Restated By-laws, appointed Mr. Scott M. Ferris as a Class III Director to fill the vacancy created by this increase. Mr. Ferris was also appointed to the Board’s Audit Committee and Operational Risk Committee. Mr. Ferris retired from BMO Financial Group in 2025, where he served as the Managing Director responsible for the commercial banking business within the Financial Institutions Group from November 2006 to January 2025. He joined BMO Harris Bank in 1985 and held various roles across commercial and corporate banking before assuming senior leadership positions within the Financial Institutions Group. Mr. Ferris brings deep expertise in credit, liquidity, market, and operational risk management, along with experience working with banking and market regulators. There was no arrangement or understanding between Mr. Ferris and any other persons pursuant to which Mr. Ferris was selected to serve as a Director of the Company. Also, Mr. Ferris has no relationships or related party transactions with the Company required to be disclosed pursuant to Item 404(a) of Regulation S-K. Other than being entitled to the compensation payable to non-employee Directors as disclosed in the Company’s proxy statement for its Annual Meeting of Shareholders on April 24, 2026, Mr. Ferris is not a party to any plans, contracts or arrangements providing for any grants, awards or other compensation payable to Mr. Ferris by the Company. The Board has determined that Mr. Ferris is an “independent director” for purposes of the applicable rules of the Nasdaq Stock Market and the Securities exchange Act of 1934, as amended.

Item 7.01 Regulation FD Disclosure. A copy of the Company’s press release, dated May 28, 2026, relating to the appointment of Mr. Ferris is furnished as Exhibit 99.1 hereto and is incorporated by reference herein.