EX-5.1

Exhibit 5.1

Wilson Sonsini Goodrich & Rosati

Professional Corporation

650 Page Mill Road

Palo Alto, CA 94304

O: (650) 493-9300

F: (650) 493-6811

March 6, 2024

Zymeworks Inc.

108 Patriot Drive, Suite A

Middletown, Delaware 19709

Re:

Registration Statement on Form S-8

Ladies and Gentlemen:

At your request, we have examined the Registration Statement on Form S-8 (the “Registration Statement”) to be filed by Zymeworks Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”), on or about the date hereof, relating to the registration under the Securities Act of 1933, as amended (the “Act”), of shares of your common stock, par value $0.00001 per share (the “Shares”), consisting of: (i) 2,804,639 shares of common stock to be issued under the Amended and Restated Stock Option and Equity Compensation Plan (the “Equity Compensation Plan”); and (ii) 419,000 shares of common stock to be issued under the Amended and Restated Employee Stock Purchase Plan (together with the Equity Compensation Plan, the “Plans”). As your legal counsel, we have reviewed the actions proposed to be taken by you in connection with the issuance and sale of the Shares to be issued under the Plans.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when issued and sold in the manner described in the Plans and pursuant to the agreements that accompany the Plans, will be validly issued, fully paid and nonassessable.

* * *

AUSTIN BEIJING BOSTON BOULDER BRUSSELS HONG KONG LONDON LOS ANGELES NEW YORK PALO ALTO

SALT LAKE CITY SAN DIEGO SAN FRANCISCO SEATTLE SHANGHAI WASHINGTON, DC WILMINGTON, DE