This summary highlights selected information in this joint proxy statement/prospectus and may not contain all of the information that is important to you. You should carefully read this entire joint proxy statement/prospectus and the other documents we refer you to for a more complete understanding of the matters being considered at the special meetings. In addition, we incorporate by reference important business and financial information about Northrim into this joint proxy statement/prospectus. You may obtain the information incorporated by reference into this joint proxy statement/prospectus without charge by following the instructions in the section entitled “Where You Can Find More Information” beginning on page 147 of this joint proxy statement/prospectus. Additionally, this summary is not a complete description of the terms and conditions of the mergers, and to gain a full understanding of such terms and conditions, you should review the merger agreement in its entirety. A copy of the merger agreement is included in this document as Annex A hereto.

Northrim is a bank holding company headquartered in Anchorage, Alaska, and serves as the holding company of Northrim Bank, an Alaska state-chartered commercial bank. Northrim Bank began banking operations in Anchorage in December 1990, and Northrim BanCorp, Inc. was formed as an Alaska corporation in connection with the reorganization into a holding company structure; that reorganization was completed effective December 31, 2001. Northrim has grown to be the third largest commercial bank in Alaska in terms of deposits. As of June 30, 2026, Northrim had 21 branches in Alaska, total assets of approximately $3.4 billion, total loans of approximately $2.4 billion, total deposits of approximately $2.9 billion and approximately $348 million in shareholders’ equity.

The business of Northrim consists primarily of accepting deposits from the general public and investing these funds in loans of various types, including commercial and real estate lending, short and medium-term commercial loans, commercial credit lines, construction and consumer loans. Northrim also originates 1-4 family residential mortgages, the majority of which are located in Alaska, most of which we sell to the secondary market. Northrim is also engaged in factoring, asset based lending, and alternative working capital lending. The mergers, if completed, will result in the first extension of Northrim’s business outside the State of Alaska.

Shares of Northrim common stock are traded on Nasdaq under the symbol “NRIM.”

For more information about Northrim, please visit Northrim’s website at www.northrim.com. The information provided on Northrim’s website (other than the documents incorporated by reference herein) is not part of this joint proxy statement/prospectus and is not incorporated herein by reference. Additional information about Northrim is included in documents incorporated by reference in this joint proxy statement/prospectus. See the section entitled “Where You Can Find More Information” on page 147.

Merger Sub is an Alaska corporation and a wholly owned subsidiary of Northrim. Merger Sub was incorporated for the sole purpose of effecting the mergers. Merger Sub will not conduct any activities other than those incidental to its formation, the execution of the merger agreement and the transactions contemplated by the merger agreement. Following the second-step merger, the separate corporate existence of Merger Sub will cease.

PBCO, an Oregon corporation headquartered in Medford, Oregon, is the holding company of PBCO Bank, an Oregon state-chartered commercial bank serving small to middle-market businesses, and individuals, throughout Southern Oregon and the Willamette Valley region. PBCO Bank was founded in 1998 and as of June 30, 2026, had total assets of

$776.6 million, total liabilities of $661.1 million and total shareholders’ equity of $115.6 million. PBCO Bank provides banking products and services, including deposit accounts, digital banking, and treasury management services, to businesses, professionals, entrepreneurs, real estate investors, and nonprofit organizations. PBCO Bank also offers a wide array of loan products, such as commercial business loans, lines of credit, SBA loans, commercial real estate loans, agribusiness loans, home equity lines of credit, and construction loans. PBCO Bank owns Steelhead Finance, an accounts receivable factoring company headquartered in Medford, Oregon. Steelhead Finance supports the transportation industry throughout the United States by providing cash flow and backroom management services to carriers and freight brokers.

PBCO Financial Corporation common stock is traded on OTCID under the symbol “PBCO.”

For more information about PBCO, please visit PBCO’s website at www.peoplesbank.bank. The information provided on PBCO’s website (other than the documents incorporated by reference herein) is not part of this joint proxy statement/prospectus and is not incorporated herein by reference. Additional information about PBCO is included in documents incorporated by reference in this joint proxy statement/prospectus. See the section entitled “Where You Can Find More Information” beginning on page 147.

The terms and conditions of the mergers are contained in the merger agreement, a copy of which is attached as Annex A to this joint proxy statement/prospectus. You are encouraged to read the merger agreement carefully and in its entirety, as it is the primary legal document that governs the mergers. The descriptions set forth in this Summary and elsewhere in this prospectus/joint proxy statement are not, in and of themselves, binding, and to gain a complete understanding of the binding terms, you should review the merger agreement itself.

Pursuant to the terms and subject to the conditions set forth in the merger agreement, at the effective time, in the merger, PBCO will merge with and into Merger Sub, with Merger Sub continuing as the surviving corporation in the merger. Immediately following the merger, in the second step merger, Merger Sub will merge with and into Northrim, with Northrim as the surviving entity. Promptly following the completion of the mergers, in the bank merger, PBCO Bank, a wholly owned subsidiary of PBCO, will merge with and into Northrim Bank, a wholly owned subsidiary of Northrim, with Northrim Bank as the surviving bank. After the effective time, Northrim shareholders will continue to own their existing shares of Northrim common stock and PBCO will cease to exist.

Each share of PBCO common stock issued and outstanding immediately prior to the effective time (except for certain shares held by PBCO (in each case other than shares held in trust accounts, managed accounts, mutual funds and the like, or otherwise held in a fiduciary or agency capacity or as a result of debts previously contracted) or by a PBCO shareholder who properly exercises dissenters’ rights) will be converted into the right to receive 1.160 shares of Northrim common stock, subject to adjustment under the merger agreement. PBCO shareholders who would otherwise be entitled to a fraction of a share of Northrim common stock will receive an amount in cash (rounded to the nearest cent) based on the Northrim closing share value.

Under the terms of the merger agreement, PBCO is required to have adjusted tangible common equity (which excludes accumulated other comprehensive loss (or gain), intangible assets and up to $7,500,000 of merger costs of PBCO) as of the tangible equity measuring date of not less than $102,542,499. To the extent that PBCO’s adjusted tangible common equity, as finally determined under the provision of the merger agreement, is less than $102,542,499, then the exchange ratio will be reduced on a per share basis by an amount (rounded to the nearest thousandth) determined by dividing the amount by which PBCO’s adjusted tangible common equity is less than $102,542,499 by the Northrim closing share value, and then dividing that result by the number of shares of PBCO common stock outstanding. As of June 30, 2026, PBCO’s estimated adjusted tangible common equity was $103,657,844.

Northrim common stock is listed on Nasdaq under the symbol “NRIM,” and PBCO common stock is quoted on the OTCID under the symbol “PBCO.” The following table shows the closing sale prices of Northrim common stock and PBCO common stock as reported on Nasdaq and the OTCID, respectively, on July 21, 2026, the last trading day before the public announcement of the merger agreement, and on September 16, 2026, the last practicable trading day before the date of this joint proxy statement/prospectus. This table also shows the implied value of the merger consideration to be issued in exchange for each share of PBCO common stock, which was calculated by multiplying the closing price of Northrim common stock on those dates by the exchange ratio of 1.160 rounded to the nearest cent.

For more information on the exchange ratio, see the section entitled “The Mergers—Terms of the Mergers” beginning on page 51 and the section entitled “The Merger Agreement—Merger Consideration” beginning on page 93.

PBCO has granted restricted stock, RSUs and phantom units as additional compensation to various directors, executive officers, and other employees. As of September 9, 2026, PBCO had 14,326 shares of restricted stock, 61,913 RSUs and 35,613 phantom units outstanding. In connection with the merger, outstanding equity awards will be treated as follows at the effective time:

The mergers, taken together, are intended to qualify as a “reorganization” within the meaning of Section 368(a) of the Code for U.S. federal income tax purposes, and it is a condition to our respective obligations to complete the merger that each of Northrim and PBCO receives a legal opinion to the effect that the mergers, taken together, should so qualify. Presuming that the mergers so qualify, PBCO shareholders generally are not expected to recognize any gain or loss for U.S. federal income tax purposes on the exchange of PBCO common stock for Northrim common stock in the merger, except for any gain or loss that may result from the receipt of cash instead of a fractional share of Northrim common stock. You should be aware that the tax consequences of the mergers may depend upon your own situation. In addition, you may be subject to U.S. federal tax laws other than U.S. federal income tax laws and to state, local or non-U.S. tax laws that are not discussed in this joint proxy statement/prospectus. You should therefore consult with your own tax advisor for a full understanding of the tax consequences to you of the mergers.

For more detailed information, please refer to the section entitled “Material U.S. Federal Income Tax Consequences of the Mergers” beginning on page 111.

The U.S. federal income tax consequences described above may not apply to all PBCO shareholders. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your tax advisor for a full understanding of the particular tax consequences of the mergers to you.

After careful consideration, the Northrim board of directors, at a special meeting held on July 21, 2026, unanimously (i) determined that the merger agreement and the transactions contemplated thereby, including the mergers and the Northrim share issuance, are advisable and fair to and in the best interests of Northrim and its shareholders and (ii) approved the execution, delivery and performance of the merger agreement and the consummation of the transactions contemplated thereby, including the mergers and the Northrim share issuance. Accordingly, the Northrim board of directors unanimously recommends that the Northrim shareholders vote “FOR” the Northrim share issuance proposal and “FOR” the Northrim adjournment proposal. For a more detailed discussion of the Northrim board of directors’ recommendation, see the section entitled “The Mergers—Northrim’s Reasons for the Mergers; Recommendation of the Northrim Board of Directors” beginning on page 56.

Hovde Group, LLC (“Hovde”) acted as financial advisor to Northrim in connection with the proposed merger. As part of its engagement, representatives of Hovde attended the meeting of the Northrim board of directors held on July 21, 2026, at which the Northrim board of directors evaluated the proposed merger and the merger agreement. At this meeting, Hovde reviewed the financial aspects of the proposed merger and provided its opinion that, as of such date, the exchange ratio was fair to Northrim from a financial point of view. The full text of Hovde’s opinion is attached as Annex B to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by Hovde in rendering its opinion. Holders of Northrim common stock are urged to read the entire opinion carefully in connection with their consideration of the proposed merger.

Hovde’s opinion was directed to the Northrim board of directors in connection with its consideration of the merger and the merger agreement and does not constitute a recommendation to any shareholder of Northrim as to how any such shareholder should vote at any meeting of shareholders called to consider and vote upon the approval of the merger and the merger agreement or the issuance of Northrim common stock in connection with the merger. Hovde’s opinion was directed only to the fairness, from a financial point of view, of the exchange ratio to Northrim and did not address the underlying business decision of Northrim to engage in the merger, the form or structure of the merger or any other transactions contemplated in the merger agreement, the relative merits of the merger as compared to any other alternative transactions or business strategies that might exist for Northrim or the effect of any other transaction in which Northrim might engage.

For more information, see the section entitled “The Mergers—Opinion of Northrim’s Financial Advisor” beginning on page 58 and Annex B to this joint proxy statement/prospectus.

After careful consideration, at a meeting held on July 21, 2026, the PBCO board determined that the merger agreement and the transactions contemplated thereby (including the merger agreement and the bank merger agreement) are both fair and in the best interests of PBCO and its shareholders. Accordingly, the PBCO board approved and adopted the merger agreement and unanimously recommends that the PBCO shareholders vote “FOR” the PBCO merger proposal.

In reaching a determination to approve and adopt the merger agreement and recommend that the PBCO shareholders vote “FOR” the PBCO merger proposal, the PBCO board consulted with the senior management of PBCO, as well as PBCO’s financial and legal advisors, and considered a number of factors in reaching its decision, including, without limitation, the PBCO board of directors’ understanding of, and presentations of PBCO’s management and Davidson regarding the business capabilities, earnings and growth prospects, current and projected financial and regulatory condition, assets, results of operations, business strategy and current and prospective regulatory environment of both PBCO and Northrim; the current and prospective environment in which PBCO operates; the process through which the PBCO board of directors, with the assistance of management and PBCO’s financial and legal advisors, conducted extensive analysis and considered the available alternatives and the PBCO board of directors’ determination that no such alternative was as strategically and financially compelling as the proposed transaction with Northrim; the financial information and analyses presented by Davidson to the PBCO board of directors, and Davidson’s fairness opinion; the fact that the merger consideration is to be paid in the form of shares of Northrim common stock, will provide PBCO’s shareholders the opportunity to participate in any future earnings or growth of the combined company and future appreciation in the value of the combined company common stock following the mergers; the combined company will offer greater access to liquidity for the combined shareholders as Northrim common stock is traded on the Nasdaq;

Northrim’s historical cash dividend payments; the availability of statutory dissenters’ rights to PBCO shareholders; PBCO’s closing condition in the merger agreement that Hunton shall have rendered its opinion that the mergers should qualify as a “reorganization” within Section 368(a) of the Code; the results of PBCO’s due diligence investigation of Northrim; the belief that the two companies’ corporate cultures and business philosophies are complementary and compatible; the view that management of Northrim has integration experience through various acquisitions; that the mergers will result in a combined company with greater financial resources and a higher lending limit than PBCO would have if it were to continue its operations as an independent entity; the anticipated cost savings from expected increases in operating efficiency; the lack of geographic overlap between PBCO and Northrim, which will expand and diversify the markets in which the combined company operates; Northrim’s commitment to enhancing its strategic position in PBCO’s markets; management’s view that Northrim’s greater resources provide the combined company greater resiliency; the combined breadth and depth of management will strengthen the resulting team’s expertise and its ability to offset staffing deficiencies and succession issues and offer greater bench strength; PBCO’s management’s view that the mergers will allow for greater opportunities for PBCO’s clients, customers and other constituencies within the communities in which PBCO operates; the recommendation of PBCO’s management in favor of the mergers; that upon consummation of the mergers, Northrim’s and Northrim Bank’s boards of directors will each contain a current member of the PBCO board of directors; that the terms and conditions of the merger agreement are conducive to consummation of the mergers while being reasonably intended to preserve PBCO’s business; the likelihood that the mergers will be completed; Northrim’s obligation to consummate the mergers despite regulatory conditions unless such requirements represent a “materially burdensome regulatory condition”; that the merger agreement provides PBCO with the ability to seek specific performance by Northrim of its obligations under the merger agreement; subject to certain limits set forth in the merger agreement, the merger consideration is a fixed exchange ratio of shares of PBCO common stock to Northrim common stock; a price protection provision in the merger agreement; that the employees of PBCO and PBCO Bank whose employment is eliminated as a result of the mergers, subject to certain exceptions, will receive severance from Northrim; that for a period of one (1) year following the effective time of the mergers, Northrim will provide employees who remain with Northrim with (i) base salary or wages no less favorable than those the employee received prior to the effective time of the mergers, (ii) annual cash incentive compensation opportunities substantially comparable to those provided to Northrim employees, and (iii) employee benefits substantially comparable in the aggregate to those benefits provided to similarly situated employees of Northrim; and the ability of the PBCO board of directors to withdraw its recommendation that PBCO’s shareholders vote to approve the merger agreement for a superior proposal, subject to the terms and conditions set forth in the merger agreement (including the payment of a termination fee).

In considering these, and other reasons, the PBCO board of directors also weighed a variety of potential risks, including, without limitation, the possibility that the mergers may not be completed, or that its completion may be unduly delayed, for reasons beyond the control of PBCO or Northrim; the possibility that anticipated benefits of the mergers may not be realized; the risk that the merger consideration to be paid to PBCO shareholders in connection with the merger agreement could be adversely affected by a decrease in the trading price of Northrim common stock before the effective time or PBCO’s adjusted tangible common equity; the approvals required by PBCO shareholders and Northrim shareholders to complete the mergers; the requirement that PBCO conduct its business in the ordinary course and the other restrictions on the conduct of PBCO’s business prior to completion of the mergers, which may delay or prevent PBCO from undertaking business opportunities that may arise pending completion of the mergers; certain tax effects for any cash payments paid to PBCO directors, officers, employees, or shareholders as a result of the mergers; the lack of a reverse termination fee if the merger agreement is terminated for certain reasons; the transaction costs and expenses that will be incurred in connection with the mergers; risks associated with the combined business and the integration of PBCO and Northrim; and the interests that certain officers and directors of PBCO have in the mergers.

For a more detailed discussion of the PBCO board of directors’ recommendation, see “The Mergers—PBCO’s Reasons for the Mergers; Recommendation of the PBCO Board of Directors” beginning on page 66.

At the July 21, 2026 meeting of the board of directors of PBCO, a representative of PBCO’s financial advisor, D.A. Davidson & Co. (“Davidson”), rendered Davidson’s oral opinion, which was subsequently confirmed by delivery of a written opinion to the board of directors of PBCO, dated July 21, 2026, as to the fairness, from a financial point of view, of the exchange ratio in the merger to the PBCO shareholders, based upon and subject to the qualifications, assumptions and other matters considered in connection with the preparation of its opinion.

The full text of the written opinion of Davidson, dated July 21, 2026, which sets forth, among other things, the various qualifications, assumptions and limitations on the scope of the review undertaken by Davidson, is attached as Annex C to this joint proxy statement/prospectus. Davidson provided its opinion for the information and assistance of the board of directors of PBCO (solely in its capacity as such) in connection with, and for purposes of, PBCO’s consideration of the financial terms of the merger and Davidson’s opinion only addressed whether the exchange ratio was fair, from a financial point of view, to the PBCO shareholders. The opinion of Davidson does not address any other term or aspect of the merger agreement, or any transactions contemplated thereby. Davidson’s opinion does not address the underlying business decision of PBCO to engage in the merger or constitute a recommendation to the board of directors of PBCO or any PBCO shareholders as to how the board of directors of PBCO, such shareholder or any other person should vote or otherwise act with respect to the merger or any other matter.

For more information, see the section entitled “The Mergers—Opinion of PBCO’s Financial Advisor” beginning on page 70 and Annex C to this joint proxy statement/prospectus.

Northrim’s directors and executive officers as of immediately prior to the effective time are expected to continue to serve as directors or executive officers, as applicable, of the surviving entity and the surviving bank following the effective time. Other than the foregoing, Northrim’s directors and executive officers do not have any interests in the mergers that may be different from, or in addition to, the interests of Northrim shareholders generally.

In considering the information contained in this proxy statement/prospectus, you should be aware that PBCO’s directors and executive officers have interests in the mergers that are different from, or in addition to, the interests of PBCO shareholders generally. The PBCO board of directors was aware of these interests and considered them, among other things, in approving the merger agreement. These interests include, among other things:

The PBCO board of directors was aware of these interests and considered them, among other matters, in making its recommendation that PBCO shareholders vote to approve the PBCO merger proposal and the PBCO adjournment proposal.

For more information, see “The Mergers—Background of the Mergers” beginning on page 51 and “The Mergers—PBCO’s Reasons for the Mergers; Recommendation of the PBCO Board of Directors” beginning on page 66. These interests are described in more detail below, and certain of them are quantified in the narrative and in the section entitled “The Mergers—Interests of Certain PBCO Directors and Executive Officers in the Mergers” beginning on page 85.

On July 22, 2026, Northrim and certain directors of PBCO entered into a voting and support agreement. Under the voting and support agreement, the PBCO directors have agreed to vote all of their shares of PBCO common stock in

favor of the merger agreement. The voting and support agreement covers 1,996,879 shares, or approximately 39.37% of PBCO’s outstanding shares of common stock as of the record date for the special meeting. The PBCO directors have also agreed to certain non-competition and non-solicit obligations in favor of Northrim and Northrim Bank following the completion of the mergers. This voting and support agreement terminates if the merger agreement is terminated in accordance with its terms. A copy of voting and support agreement is attached as Exhibit B to Annex A to this joint proxy statement/prospectus.

On July 22, 2026, Northrim and certain directors and executive officers of PBCO, in their capacities as shareholders of PBCO, entered into a support agreement. Under the support agreement, the PBCO directors and executive officers have agreed to certain non-competition obligations and certain directors and executive officers have agreed to non-solicit obligations in favor of Northrim and Northrim Bank following the completion of the mergers. This support agreement terminates if the merger agreement is terminated in accordance with its terms. A copy of support agreement is attached as Exhibit C to Annex A to this joint proxy statement/prospectus.

In addition, as a condition to Northrim entering into the merger agreement, certain employees of PBCO entered into employment agreements with Northrim and Northrim Bank, to become effective upon the consummation of the merger.

At the effective time, one legacy PBCO director, expected to be James E. Teece, mutually agreed to by Northrim and PBCO, will become a member of the board of directors of Northrim and the board of directors of Northrim Bank. Michael G. Huston, the current Chairman of the Northrim board of directors and the Northrim Bank board of directors, will continue to serve as the Chairman of the Northrim board of directors and the Northrim Bank board of directors and each of the members of the Northrim and Northrim Bank boards of directors as of immediately prior to the mergers and the bank merger will continue to serve on the Northrim and Northrim Bank boards of directors.

Michael G. Huston will continue to serve as Chairman, President, Chief Executive Officer and Chief Operating Officer of Northrim and Chairman, President and Chief Executive Officer of Northrim Bank and each of the executive officers of Northrim and Northrim Bank as of immediately prior to the mergers and the bank merger will continue to serve in the same positions of Northrim and Northrim Bank following the mergers and the bank merger.

Subject to the terms of the merger agreement, Northrim and PBCO have agreed to cooperate with each other and use their reasonable best efforts to promptly prepare and file all necessary documentation, to effect all applications, notices, petitions and filings (and, in the case of the applications, notices, petitions and filings in respect of the requisite regulatory approvals, use their reasonable best efforts to make such filings within 45 calendar days of the date of the merger agreement), to obtain as promptly as practicable all permits, consents, approvals and authorizations of all third parties and governmental entities that are necessary or advisable to consummate the mergers, the bank merger and the other transactions contemplated by the merger agreement, and to comply with the terms and conditions of all such permits, consents, approvals and authorizations of all such third parties or governmental entities. These approvals include, among others, the approval of the Board of Governors of the Federal Reserve System (the “Federal Reserve Board”), the Federal Deposit Insurance Corporation (the “FDIC”), the Alaska Department of Commerce, Community, and Economic Development, Division of Banking and Securities (the “ADBS”), and the Oregon Department of Consumer and Business Services, Division of Financial Regulation (the “DCBS”). The initial submission of these regulatory applications occurred on September 3, 2026. Additional notifications and/or applications requesting approval may be submitted to various other federal, state and non-U.S. regulatory authorities and self-regulatory organizations.

Although neither Northrim nor PBCO knows of any reason why it cannot obtain these regulatory approvals in a timely manner, Northrim and PBCO cannot be certain when or if they will be obtained, or that the granting of these regulatory approvals will not involve the imposition of conditions on the completion of the mergers or the bank merger.

Neither Northrim nor PBCO can predict the actual date on which the merger will be completed, or if the merger will be completed at all, because completion is subject to conditions and factors outside the control of both companies. Northrim must first obtain the requisite Northrim shareholder approval and PBCO must first obtain the requisite PBCO

shareholder approval. Northrim and PBCO must also obtain the requisite regulatory approvals and satisfy certain other closing conditions. Northrim and PBCO expect the merger to be completed promptly once Northrim has obtained the requisite Northrim shareholder approval, PBCO has obtained the requisite PBCO shareholder, the requisite regulatory approvals have been obtained and other closing conditions are satisfied. The second step merger is expected to be completed immediately following the completion of the merger.

Under the terms of the merger agreement, PBCO is required to have adjusted tangible common equity (which excludes accumulated other comprehensive loss (or gain), intangible assets and up to $7,500,000 of merger costs of PBCO) as of the tangible equity measuring date of not less than $102,542,499. To the extent that PBCO’s adjusted tangible common equity, as finally determined under the provision of the merger agreement, is less than $102,542,499, then the exchange ratio will be reduced on a per share basis by an amount (rounded to the nearest thousandth) determined by dividing the amount by which PBCO’s adjusted tangible common equity is less than $102,542,499 by the Northrim closing share value, and then dividing that result by the number of shares of PBCO common stock outstanding. As of June 30, 2026, PBCO’s estimated adjusted tangible common equity was $103,657,844.

As more fully described in this joint proxy statement/prospectus and in the merger agreement, the completion of the merger depends on a number of conditions being satisfied or waived. These conditions include:

Neither Northrim nor PBCO can provide assurance as to when or if all of the conditions to the merger can or will be satisfied or waived by the appropriate party.

Each of Northrim and PBCO has agreed that it will, and will cause each of its subsidiaries and representatives to, immediately cease, and cause to be terminated, any activities, discussions or negotiations conducted before the date of the merger agreement with any person other than PBCO, in the case of Northrim, or Northrim, in the case of PBCO, with respect to any acquisition proposal, as such term is used in the merger agreement.

Each of Northrim and PBCO has agreed that it will not, and will cause each of its subsidiaries and use its reasonable best efforts to cause its and their respective officers, directors, employees, agents, advisors and representatives not to, directly or indirectly, (i) solicit, initiate, or knowingly encourage (including by way of knowingly furnishing information or assistance), or knowingly facilitate any inquiries or the making of any proposal or offer concerning an acquisition proposal, (ii) provide any confidential information or data to any person relating to any acquisition proposal, (iii) participate in any discussions or negotiations regarding any acquisition proposal, (iv) unless the merger agreement has been terminated in accordance with its terms, approve or recommend, propose to approve or recommend, or execute or enter into, any letter of intent, agreement in principle, merger agreement, asset purchase agreement or share exchange agreement, option agreement or other similar agreement (whether written or oral, binding or nonbinding) related to any acquisition proposal or propose to do any of the foregoing, or make or authorize any statement, recommendation or solicitation in support of any acquisition proposal. See the section entitled “The Merger Agreement—Agreement Not to Solicit Other Offers” beginning on page 103 for additional information regarding the meaning of an “acquisition proposal”;

The merger agreement can be terminated at any time prior to the effective time, whether before or after receipt of the requisite PBCO shareholder approval or the requisite Northrim shareholder approval, in the following circumstances:

If the merger agreement is terminated by either Northrim or PBCO under certain circumstances, including certain circumstances involving alternative acquisition proposals and changes in the recommendations of PBCO’s board, PBCO will be required to pay a termination fee to Northrim equal to approximately $6.7 million.

The mergers will be accounted for as an acquisition of PBCO by Northrim under the acquisition method of accounting in accordance with the U.S. generally accepted accounting principles (“GAAP”).

Upon completion of the merger, the rights of former PBCO shareholders who receive shares of Northrim common stock in the merger and who thereby become Northrim shareholders will be governed by the Northrim articles and the Northrim bylaws. The rights associated with PBCO common stock are different from the rights associated with Northrim common stock. In addition, the rights of shareholders under Alaska law, where Northrim is organized, may differ from the rights of shareholders under Oregon law, where PBCO is organized. See the section entitled “Comparison of the Rights of Northrim Shareholders and PBCO shareholders” on page 133 for a discussion of the different rights associated with PBCO common stock and Northrim common stock.

The shares of Northrim common stock to be issued in the merger will be listed for trading on Nasdaq. Following the mergers, shares of Northrim common stock will continue to be traded on Nasdaq. In addition, following the merger, PBCO common stock will be delisted from the OTCID.

The Northrim special meeting will be held virtually via the internet on October 20, 2026 at 9:00 a.m., Alaska Time. At the Northrim special meeting, Northrim shareholders will be asked to vote on the following matters:

You may vote at the Northrim special meeting if you owned shares of Northrim common stock at the close of business on September 9, 2026. As of September 9, 2026, there were 22,244,766 shares of Northrim common stock outstanding,

of which approximately 2% were owned and entitled to be voted by Northrim directors and executive officers and their affiliates. We currently expect that Northrim’s directors and executive officers will vote their shares in favor of the Northrim share issuance proposal and the Northrim adjournment proposal, although none of them has entered into any agreements obligating them to do so.

The Northrim share issuance proposal will be approved if the affirmative vote of the holders of a majority of the outstanding shares of Northrim common stock entitled to vote, represented virtually or by proxy, approves the share issuance proposal at the Northrim special meeting. If a Northrim shareholder present at the Northrim special meeting abstains from voting, or responds by proxy with an “ABSTAIN,” it will have the same effect as a vote against the proposal to approve the share issuance proposal. If a Northrim shareholder does not respond by proxy or does not provide his, her or its bank, broker, trustee or other nominee with instructions, as applicable, it will have the same effect as a vote against the proposal to approve the share issuance proposal.

The Northrim adjournment proposal will be approved if the number of votes cast favoring the Northrim adjournment proposal exceeds the number of votes cast opposing the Northrim adjournment proposal at the Northrim special meeting, whether or not a quorum is present. If a Northrim shareholder present at the Northrim special meeting abstains from voting, or responds by proxy with an “ABSTAIN,” it will have the no effect on such proposal. If a Northrim shareholder does not respond by proxy or does not provide his, her or its bank, broker, trustee or other nominee with instructions, as applicable, it will have the no effect on such proposal.

The PBCO special meeting will be held at 2:00 p.m., Pacific Time, on October 20, 2026 at Rogue Valley Country Club, 2660 Hillcrest Road, Medford, Oregon 97504. At the PBCO special meeting, holders of PBCO common stock will be asked to consider and vote on the following proposals:

The board of directors of PBCO has fixed the close of business on September 9, 2026 as the record date for determining the shareholders entitled to notice of, and to vote at, the PBCO special meeting and any adjournments or postponements of the PBCO special meeting. Approval of the PBCO merger proposal requires the affirmative vote of a majority of all of the votes entitled to be cast on the merger agreement. Approval of the PBCO adjournment proposal requires the affirmative vote of the votes cast at the PBCO special meeting by holders of PBCO common stock entitled to vote at the PBCO special meeting.

On the record date for the PBCO special meeting, there were 5,072,054 shares of PBCO common stock outstanding, of which approximately 53.78% were owned and entitled to be voted by PBCO directors and executive officers and their affiliates.

In connection with the merger agreement, certain directors of PBCO entered into a voting and support agreement. Under the voting and support agreement, the PBCO directors have agreed to vote all of their shares of PBCO common stock in favor of the merger agreement. The voting and support agreement covers 1,996,879 shares, or approximately 39.37% of PBCO’s outstanding shares of common stock as of the record date for the special meeting.

If you mark “ABSTAIN” on your proxy, fail to submit a proxy or vote at the PBCO special meeting, or fail to instruct your bank, broker, trustee, or other nominee how to vote with respect to the PBCO merger proposal, it will have the same effect as a vote “AGAINST” the PBCO merger proposal. If you mark “ABSTAIN” on your proxy, it will have no effect on the PBCO adjournment proposal. If you fail to submit a proxy or vote at the PBCO special meeting, or fail to instruct your bank, broker, trustee, or other nominee how to vote with respect to the PBCO adjournment proposal, it will have no effect on the PBCO adjournment proposal.

PBCO shareholders are entitled to dissenters’ rights under the OBCA. Northrim shareholders are not entitled to dissenters’ rights under the ACC. For more information, see the section entitled “The Mergers—Dissenters’ Rights in Connection with the Mergers” beginning on page 90.

In evaluating the merger agreement, the mergers or the issuance of shares of Northrim common stock, you should carefully read this joint proxy statement/prospectus and give special consideration to the factors discussed in the section entitled “Risk Factors” beginning on page 29.