Bank of Marin Bancorp

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934 (Amendment No. )

Payment of Filing Fee (Check the appropriate box):

Notice of Annual Meeting of Shareholders

Bank of Marin Bancorp

Tuesday, May 14, 2024 – 6:00 p.m. Pacific Time

To Our Shareholders:

Notice is hereby given of the Annual Meeting of Shareholders of Bank of Marin Bancorp. The meeting will be held at 6:00 p.m. on Tuesday, May 14, 2024 at the Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, California. A reception at the Buck Institute for Research on Aging will immediately follow the Annual Meeting.

Your vote is important to us. Whether or not you expect to attend the Annual Meeting, please submit a proxy as soon as possible to instruct how your shares are to be voted at the Annual Meeting. If you participate in and vote your shares at the Annual Meeting, your proxy will not be used.

If you would like to attend the Annual Meeting, you must pre-register atwww.bankofmarin.com/annual**** meeting by May 7, 2024. For questions, emailevents @bankofmarin.com.

Our bylaws provide that nominations for election to the board of directors of the Company may be made by the board of directors or by any shareholder of the Company’s stock entitled to vote for the election of directors. Nominations, other than those made by or on behalf of the existing management of the Company, must be made in writing and delivered or mailed to the Chairman of the Board or the Chief Executive Officer not less than 14 days nor more than 50 days prior to any meeting of shareholders called for the election of directors. The notification of nomination should contain the following information to the extent known by the notifying shareholder: (a) name and address of the proposed nominee(s); (b) principal occupation of the proposed nominee(s); (c) total number of shares that will be voted for the proposed nominee(s); (d) name and residence address of the notifying shareholder; and (e) number of shares owned by the notifying shareholder. Nominations not made in accordance with this section may be disregarded by the Chairman of the meeting, and upon instruction, the Inspector of Election shall disregard all votes cast for each such nominee.

One copy of the Annual Report on Form 10-K and Proxy Statement is being delivered to multiple shareholders sharing an address unless the Company has received contrary instructions from one or more of the shareholders. The Company will deliver promptly upon written or oral request a separate copy of the Annual Report and Proxy Statement to a shareholder at a shared address to which a single copy of the document was delivered. If a shareholder wishes to receive a separate copy or has received multiple copies at one address and would like to receive a single copy in the future, please contact Computershare Trust Company, N.A. by phone at (800) 368-5948 or by written request to Bank of Marin Bancorp c/o Computershare Trust Company, N.A., P.O. Box 43006, Providence, RI 02940-3006. Overnight correspondence should be mailed to Bank of Marin Bancorp c/o Computershare, 150 Royall St., Suite 101, Canton MA 02021. The shareholder website iswww.computershare.com/investor.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE

MEETING OF SHAREHOLDERS TO BE HELD ON MAY 14, 2024

Copies of the Annual Meeting Proxy Material, including the Proxy Statement and the Annual Report on Form 10- K, are also available at:www.edocumentview.com/BMRC.

By order of the Board of Directors,

Krissy Meyer

Secretary

April 9, 2024