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

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐ 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 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)

Payment of Filing Fee (Check all boxes that apply):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

Your Vote Counts! CTS CORPORATION 2024 Annual Meeting Vote by May 8, 2024 11:59 PM ET CTS CORPORATION ATTN: SCOTT D’ANGELO 4925 INDIANA AVENUE LISLE, IL 60532 V33548-P00677 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 9, 2024. 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 them prior to April 25, 2024. 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. For complete information and to vote, visit www.ProxyVote.com Control # Smartphone users Vote in Person at the Meeting* Point your camera here and vote without entering a control number May 9, 2024 9:30 a.m. Central Time 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.

Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming Annual Meeting. Please follow the instructions on the reverse side to vote on these important matters. Voting Items Board Recommends 1. Election of Directors Nominees: 1a. D. M. Costello For 1b. A. M. Dodrill For 1c. W. S. Johnson For 1d. K. M. O’Sullivan For 1e. R. A. Profusek For 1f. R. Stone For 1g. A. G. Zulueta For 2. Approval, on an advisory basis, of the compensation of CTS’ named executive officers. For 3. Ratification of the appointment of Grant Thornton LLP as CTS’ independent auditor for 2024. For 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. Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. V33549-P00677