Exhibit 5.2

[Letterhead of Sullivan & Cromwell LLP]

December 29, 2021

Columbia Banking System, Inc.,

1301 A Street,

Tacoma, Washington 98402.

Ladies and Gentlemen:

We are acting as counsel to Columbia Banking System, Inc., a Washington corporation (the “Company”), in connection with its filing of a registration statement on Form S-3 (the “Registration Statement”) under the Securities Act of 1933 (the “Act”). The Registration Statement registers common stock, no par value, of the Company, preferred stock, no par value, of the Company, depositary shares representing preferred stock (the “Depositary Shares”), senior and subordinated debt securities (the “Debt Securities”), purchase contracts (the “Purchase Contracts”), warrants to purchase Common Stock, Preferred Stock, Depositary Shares, Debt Securities or Units (as defined below) (the “Warrants”), and units comprised of two or more of the foregoing (the “Units,” and together with the Common Stock, Preferred Stock, Depositary Shares, Debt Securities or Warrants, the “Securities”).

In connection with the filing of the Registration Statement, we, as your counsel, have examined such corporate records, certificates and other documents, and such questions of law, as we have considered necessary or appropriate for the purposes of this opinion. Upon the basis of such examination, it is our opinion that:

(1) Debt Securities. When the Registration Statement has become effective under the Act, when the applicable indenture (the “Debt Indenture”) relating to the Debt Securities has been duly authorized, executed and delivered, when the terms of the Debt Securities and of their issuance and sale have been duly established in conformity with the applicable Debt Indenture, so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company, and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, and when the Debt Securities have been duly executed and authenticated in accordance with the applicable Debt Indenture and issued and sold as contemplated in the Registration Statement, and if all the foregoing actions are taken pursuant to authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, the Debt Securities will constitute valid and legally binding obligations of the Company, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles. The Debt Securities covered by the opinion in this paragraph include any Debt Securities that may be issued as part of the Units or upon exercise or otherwise pursuant to the terms of any other Securities as well as any Purchase Contracts or Units that may be issued under the applicable Debt Indenture relating to the Debt Securities.

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(2) Depositary Shares. When the Registration Statement has become effective under the Act, when the terms of any applicable deposit agreements under which the Depositary Shares are to be issued have been duly established and any applicable deposit agreements have been duly authorized, executed and delivered, when the terms of the Depositary Shares and of their issuance and sale have been duly established in conformity with the applicable deposit agreements, when the Preferred Stock represented by the Depositary Shares have been duly delivered to the applicable depositaries and when the depositary receipts evidencing the Depositary Shares have been duly issued against deposit of the Preferred Stock in accordance with the applicable deposit agreements and issued and sold as contemplated by the Registration Statement, and if all the foregoing actions are taken pursuant to authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, and so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, the depositary receipts evidencing the Depositary Shares will be validly issued and will entitle the holders thereof to the rights specified in the Depositary Shares and the applicable deposit agreements, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles. The Depositary Shares covered by the opinion in this paragraph include any Depositary Shares that may be issued as part of the Units or upon exercise or otherwise pursuant to the terms of any other Securities.

(3) Warrants. When the Registration Statement has become effective under the Act, when the terms of any applicable warrant agreements under which the Warrants are to be issued have been duly established and the applicable warrant agreements have been duly authorized, executed and delivered, when the terms of the Warrants and of their issuance and sale have been duly established in conformity with the applicable warrant agreement and when the Warrants have been duly executed and authenticated in accordance with the applicable warrant agreement and issued and sold as contemplated by the Registration Statement, and if all the foregoing actions are taken pursuant to authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, and so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, the Warrants will constitute valid and legally binding obligations of the Company, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles. The Warrants covered by the opinion in this paragraph include any Warrants that may be issued as part of the Units or upon exercise or otherwise pursuant to the terms of any other Securities.

(4) Purchase Contracts. When the Registration Statement has become effective under the Act, when the terms of the governing instruments or agreements under which certain of the Purchase Contracts are to be issued have been duly established and the governing documents have been duly authorized, executed and delivered, when the terms of the Purchase Contracts and of their issuance and sale have been duly established in conformity with the applicable governing documents and when the Purchase Contracts have been duly executed and authenticated in accordance with the applicable governing documents and issued and sold as contemplated in the Registration Statement, and if all the foregoing actions are taken pursuant to authority granted in resolutions duly adopted by the Company’s Board of Directors or a duly authorized committee thereof, and so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, the Purchase Contracts will constitute valid and legally binding obligations of the Company, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles. The Purchase Contracts covered by the opinion in this paragraph include any Purchase Contracts that may be issued as part of the Units or upon exercise or otherwise pursuant to the terms of any other Securities.

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(5) Units. When the Registration Statement has become effective under the Act, when the terms of the unit agreements under which the Units are to be issued have been duly established and the unit agreements have been duly authorized, executed and delivered, when the terms of the Units and of their issuance and sale have been duly established in conformity with the applicable unit agreements and when the Units have been duly executed and authenticated in accordance with the applicable unit agreements and issued and sold as contemplated in the Registration Statement, and if all the foregoing actions are taken pursuant to the authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, and so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding upon the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company, the Units will constitute valid and legally binding obligations of the Company, subject to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium and similar laws of general applicability relating to or affecting creditors’ rights and to general equity principles. The Units covered by the opinion in this paragraph include any Units that may be issued upon exercise or otherwise pursuant to the terms of any other Securities.

The foregoing opinion is limited to the Federal laws of the United States and the laws of the State of New York, and we are expressing no opinion as to the effect of the laws of any other jurisdiction. With respect to all matters of Washington law, we have relied upon the opinion, dated December 29, 2021, of Kumi Y. Baruffi, and our opinion is subject to the same assumptions, qualifications and limitations with respect to such matters as are contained in such opinion of Kumi Y. Baruffi.

In rendering the foregoing opinion, we are not passing upon, and assume no responsibility for, any disclosure in the Registration Statement or any related prospectus regarding the Company, the Securities, or their offering and sale.

We have relied as to certain factual matters on information obtained from public officials, officers of the Company and other sources believed by us to be responsible, and we have assumed all other governing documents under which the Securities are to be issued, as well as the purchase contracts, if applicable, will have been duly authorized, executed and delivered by all parties thereto other than the Company and that the signatures on documents examined by us are genuine. We have further assumed that the issuance or delivery by the Company of any securities other than the Securities, or of any other property, upon exercise or otherwise pursuant to the terms of the Securities will be effected pursuant to authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, and so as not to violate any applicable law or result in a default under or breach of any agreement or instrument binding on the Company and so as to comply with any requirement or restriction imposed by any court or governmental body having jurisdiction over the Company. Finally, we have assumed that the authority granted in resolutions duly adopted by the Company’s Board of Directors, or a duly authorized committee thereof, will remain in effect at all relevant times and that no Securities will be issued or other action taken in contravention of any applicable limit established pursuant to such resolutions from time to time.

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We are expressing no opinion as to any obligations that parties other than the Company may have under or in respect of the Securities, or as to the effect that their performance of such obligations may have upon any of the matters referred to above. Nor are we expressing an opinion as to securities of any persons other than the Company.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the reference to us under the heading “Validity of the Securities” in the prospectus contained therein. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act.

Very truly yours,

/S/ SULLIVAN & CROMWELL LLP

SULLIVAN & CROMWELL LLP