HERITAGE FINANCIAL CORP /WA/

(a) On November 6, 2025, Heritage entered into an addendum with each of Bryan McDonald, Donald Hinson, Tony Chalfant, and Nicholas Bley (collectively, the “Addenda”) that modified each such officer’s participation agreement (collectively, the “Participation Agreements”) with respect to the Heritage Financial Corporation Deferred Compensation Plan (the “DCP”). The Addenda modified the Participation Agreements by extending the period that Heritage will make annual performance-based contributions to each such officer’s “Company Contribution Account” under the DCP through the 2028 plan year.

The foregoing description of the Addenda does not purport to be complete and is qualified in its entirety by reference to the Addenda, copies of which are attached hereto as Exhibits 10.3 - 10.6 and are incorporated herein by reference, as well as the Participation Agreements, all other addenda to the Participation Agreements, and the DCP as previously disclosed.

(b) None.

(c) During the three months ended September 30, 2025, none of the Company’s directors or executive officers adopted or terminated any contract, instruction or written plan for the purchase or sale of Company securities that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) or any “non-Rule 10b5-1 trading arrangement.