Columbia Financial, Inc.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers On June 29, 2026, Columbia Financial, Inc. (the “Company”) filed a Current Report on Form 8-K (the “Initial Form 8-K”) disclosing that the Board of Directors (the “Board”) of the Company had expanded its number of authorized directors from nine to thirteen directors and appointed John P. Connors, Jr., Timothy C. Harrison, Steven M. Klein, and Paul V. Stahlin to the Board, to be effective upon the completion of the Company’s acquisition of Northfield Bancorp, Inc. (the “Merger”). The Merger was completed on July 20, 2026 and, effective upon that date, Messrs. Connors, Harrison, Klein and Stahlin became directors of the Company. Committee assignments for the new directors had not been determined as of the filing of the Initial Form 8-K. On July 28, 2026, effective immediately, the Board appointed (i) Mr. Connors to its Audit Committee, Nominating/Corporate Governance Committee, Risk Committee and Technology Committee; (ii) Mr. Harrison to its Compensation Committee, Nominating/Corporate Governance Committee, Risk Committee and Technology Committee; and (iii) Mr. Stahlin to its Audit Committee, Compensation Committee, Risk Committee and Operations and Strategic Planning Committee. In each case, the Board had previously determined that each of Messrs. Connors, Harrison and Stahlin satisfies all applicable requirements to serve on the Audit, Compensation and Nominating/Corporate Governance Committees, as applicable, including without limitation the applicable requirements of The Nasdaq Stock Market and the Securities Exchange Act of 1934, as amended. Also on July 28, 2026, effective immediately, the Board appointed Mr. Klein, who also serves as Senior Executive Vice President and Chief Operating Officer of the Company, to its Risk Committee, Operations and Strategic Planning Committee, and Technology Committee.