UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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☐ Preliminary Proxy Statement

☐ Confidential, For Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material Under §240.14a-12

NKARTA, INC.

(Name of Registrant as Specified In Its Charter)

Not applicable

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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NKARTA, INC. 6000 SHORELINE COURT, SUITE 102 SOUTH SAN FRANCISCO, CA 94080 Your Vote Counts! NKARTA, INC. 2022 Annual Meeting Vote by June 7, 2022 11:59 PM ET D75951-P67763 You invested in NKARTA, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy material for the stockholder meeting to be held on June 8, 2022. Get informed before you vote View the Proxy Statement and Annual Report on Form 10-K online OR you can receive a free paper or email copy of the material(s) by making a request prior to May 25, 2022. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. For complete information and to vote, visit www.ProxyVote.com Control # Smartphone users Point your camera here and vote without entering a control number Vote Virtually at the Meeting* June 8, 2022 9:00 a.m., Pacific Time www.virtualshareholdermeeting.com/NKTX2022 Vote Before the Meeting at ProxyVote.com by June 7, 2022 11:59 PM ET *Please check the meeting materials for any special requirements for meeting attendance.

Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote on these important matters. Voting Items Board Recommends 1. Election of three directors to serve until the company’s 2025 annual meeting of stockholders and until their respective successors are duly elected and qualified: 01) Michael Dybbs, Ph.D. 02) Simeon George, M.D., M.B.A. 03) Leone Patterson, M.B.A. For All 2. Ratification of the appointment of Ernst & Young LLP as the company’s independent registered public accounting firm for the year ending December 31, 2022. For NOTE: In their discretion, the proxies are authorized to vote upon such other business as may properly come before the meeting or any adjournment or postponement thereof. Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Sign up for E-delivery”. D75952-P67763