HERITAGE FINANCIAL CORP /WA/

Heritage filed a registration statement on Form S-4 with the SEC in connection with the proposed transaction. The registration statement includes a joint proxy statement of Heritage and Olympic that also constitutes a prospectus of Heritage, which was sent to the shareholders of Heritage and Olympic on or about December 12, 2025. Before making any voting decision, the shareholders of Heritage and Olympic are advised to read the joint proxy statement/prospectus because it contains important information about Heritage, Olympic and the proposed transaction. Documents relating to the Merger filed by Heritage can be obtained free of charge from the SEC’s website at www.sec.gov. These documents also can be obtained free of charge by accessing Heritage’s website at hf-wa.com under the tab “Financials.” Alternatively, these documents can be obtained free of charge from Heritage upon written request to Heritage Financial Corporation, Attn: Investor Relations, 201 5th Avenue Southwest, Olympia, Washington 98501, or by calling (360) 943-1550. The contents of the website referenced above are not deemed to be incorporated by reference into the registration statement or the joint proxy statement/prospectus.