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Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in Registration Statements Nos. 333-204739, 333-180163, 333-150014, and 333-120523 on Form S-8 of Costco Wholesale Corporation of our report dated June 26, 2026 appearing in this Annual Report on Form 11-K of Costco 401(k) Retirement Plan for the year ended December 31, 2025.

/s/ Crowe LLP

Oakbrook Terrace, Illinois

June 26, 2026