Exhibit 5.1

May 15, 2026

Cohu, Inc.

17087 Via Del Campo

San Diego, CA 92127-1711

Re: Registration Statements on Form S-8

Ladies and Gentlemen:

As legal counsel for Cohu, Inc., a Delaware corporation (the “Company”), we are rendering this opinion in connection with the registration on Form S-8 (the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”), of (i) 3,400,000 shares of common stock, $1.00 par value of the Company (“Common Stock”) which may be issued pursuant to the Cohu, Inc. 2026 Equity Incentive Plan (the “2026 Plan”) and (ii) 600,000 shares of Common Stock (collectively, the “Shares”), which may be issued pursuant to the Amended and Restated Cohu, Inc. 1997 Employee Stock Purchase Plan (the “ESPP”).

We have examined such instruments, documents and records which we deemed relevant and necessary for the basis of our opinion hereinafter expressed. In such examination, we have assumed the genuineness of all signatures and the authenticity of all documents submitted to us as originals and the conformity to the originals of all documents submitted to us as copies. We express no opinion concerning any law other than the corporation laws of the State of Delaware and the federal law of the United States.

Based on such examination, we are of the opinion that the Shares which may be issued under the 2026 Plan and the ESPP, when issued against receipt of the consideration therefor in accordance with the provisions of the 2026 Plan or the ESPP, as applicable, will be validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement referred to above and the use of our name wherever it appears in the Registration Statement. In giving this consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Securities and Exchange Commission promulgated thereunder.

This opinion letter is given to you solely for use in connection with the issuance of the Shares in accordance with the Registration Statement and is not to be relied on for any other purpose. Our opinion is expressly limited to the matters set forth above, and we render no opinion, whether by implication or otherwise, as to any other matters relating to the Company, the Shares, or the Registration Statement. This opinion is rendered as of the date hereof, and we assume no obligation to advise you of any fact, circumstance, event or development that may hereafter be brought to our attention whether or not such occurrence would alter, affect or modify the opinion expressed herein.

Respectfully submitted,

/s/ DLA Piper LLP (US)

DLA Piper LLP (US)