UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

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Filed by a Party other than the Registrant ¨

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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

x Definitive Additional Materials

¨ Soliciting Material Pursuant to Sec.240.14a-12

Southside Bancshares, Inc.

(Name of Registrant as Specified In Its Charter)

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

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x No fee required.

¨ Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

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¨ Fee paid previously with preliminary materials.

¨ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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IMPORTANT ANNUAL MEETING INFORMATION

	Vote by Internet
	• Go to www.investorvote.com/SBSI
	• Or scan the QR code with your smartphone
	• Follow the steps outlined on the secure website

Notice of Annual Meeting of Shareholders 1234 5678 9012 345

Important Notice Regarding the Availability of Proxy Materials for the

Southside Bancshares, Inc. Annual Meeting of Shareholders to be Held on Wednesday, May 9, 2018, 11:30 a.m., local time.

Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual shareholders’ meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy of the proxy materials. The items to be voted on and the location of the annual meeting are set forth on the reverse side. Your vote is important!

This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The proxy statement and annual report to shareholders are available at:

www.investorvote.com/SBSI

:	Easy Online Access — A Convenient Way to View Proxy Materials and Vote
	When you go online to view materials, you can also vote your shares.
	Step 1: Go to www.investorvote.com/SBSI
	Step 2: Click on the icon on the right to view current meeting materials.
	Step 3: Return to the investorvote.com window and follow the instructions on the screen to log in.
	Step 4: Make your selection as instructed on each screen to select delivery preferences and vote.

When you go online, you can also help the environment by consenting to receive electronic delivery of future materials.

4 Obtaining a Copy of the Proxy Materials – If you want to receive a copy of these documents, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed on the reverse side on or before April 27, 2018 to facilitate timely delivery.

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Notice of Annual Meeting of Shareholders

The 2018 Annual Meeting of Shareholders of Southside Bancshares, Inc. will be held at Willow Brook Country Club, 3205 West Erwin Street, Tyler, Texas, 75702 on Wednesday, May 9, 2018, at 11:30 a.m., local time.

Proposals to be voted on at the meeting are listed below, along with the Board of Directors’ recommendations.

The Board of Directors recommends a vote FOR the listed nominees and FOR Proposals 2, 3 and 4.

1. The election of S. Elaine Anderson, CPA, Herbert C. Buie, Patricia A. Callan, John R. (Bob) Garrett, and Tony K. Morgan, CPA as members of the Board of Directors of the Company to serve until the Annual Meeting of Shareholders in 2021. The election of H. J. Shands, III as a member of the Board of Directors of the Company to serve until the Annual Meeting of Shareholders in 2020. The election of M.Richard Warner as a member of the Board of Directors of the Company to serve until the Annual Meeting of Shareholders in 2019.

2. A non-binding advisory vote on the compensation of the Company's named executive officers.

3. Approval of an amendment to the certificate of formation of Southside Bancshares, Inc. to increase the number of authorized shares of common stock.

4. Ratify the appointment by our Audit Committee of Ernst & Young LLP to serve as the independent registered public accounting firm for the Company for the year ended December 31, 2018.

PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must vote online or request a paper copy of the proxy materials to receive a proxy card. If you wish to attend and vote at the meeting, please bring this notice with you.

4	Here’s how to order a copy of the proxy materials and select a future delivery preference:
	Paper copies: Current and future paper delivery requests can be submitted via the telephone, Internet or email options below.
	Email copies: Current and future email delivery requests must be submitted via the Internet following the instructions below.
	If you request an email copy of current materials you will receive an email with a link to the materials.
	PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a set of proxy materials.

àInternet – Go to www.investorvote.com/SBSI. Follow the instructions to log in and order a copy of the current meeting materials and submit your preference for email or paper delivery of future meeting materials.

àTelephone – Call us free of charge at 1-866-641-4276 and follow the instructions to log in and order a paper copy of the materials by mail for the current meeting. You can also submit a preference to receive a paper copy for future meetings.

àEmail – Send email to investorvote@computershare.com with “Proxy Materials Southside Bancshares, Inc.” in the subject line. Include in the message your full name and address, plus the number located in the shaded bar on the reverse, and state in the email that you want a paper copy of current meeting materials. You can also state your preference to receive a paper copy of materials for future meetings.

To facilitate timely delivery, all requests for a paper copy of the proxy materials must be received by April 27, 2018.