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

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☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material Pursuant to §240.14a-12

CTS CORPORATION

(Name of Registrant as Specified In Its Charter)

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

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Your Vote Counts! CTS CORPORATION ATTN: SCOTT D’ANGELO 4925 INDIANA AVENUE LISLE, IL 60532 CTS CORPORATION 2021 Annual Meeting Vote by May 12, 2021 11:59 PM ET You invested in CTS CORPORATION 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 shareholder meeting to be held on May 13, 2021. Get informed before you vote View the Notice and Proxy Statement and Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to April 29, 2021. If you would like to request a copy of the material(s) for this and/or future shareholder 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. Vote in Person at the Meeting* May 13, 2021 9:30 AM CDT Hotel Arista 2139 City Gate Lane Naperville, Illinois 60563 *Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Smartphone users Point your camera here and vote without entering a control number V1 For complete information and to vote, visit www.ProxyVote.com Control # D44377-P49843

THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming shareholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Sign up for E-delivery”. Voting Items Board Recommends D44378-P49843 01) D. M. Costello 02) G. Hunter 03) W. S. Johnson 04) Y.J. Li 05) K. O’Sullivan 06) R. A. Profusek 07) A. G. Zulueta 1. Election of Directors Nominees: 2. Approval, on an advisory basis, of the compensation of CTS’ named executive officers. 3. Ratification of the appointment of Grant Thornton LLP as CTS’ independent auditor for 2021. NOTE: In their discretion, the proxies are authorized to vote on such other business as may properly come before the meeting or any adjournment thereof. For For For