SOUTHSIDE BANCSHARES INC

If your proxy is executed and returned, it will be voted as you direct. If no direction is provided, the proxy will be voted in accordance with the Board’s recommendations, as follows:

•FOR the election of all of the nominees named in this proxy statement as directors;

•FOR the approval of the advisory vote on the compensation of the Company's named executive officers;

•FOR the approval of the 2025 Incentive Plan; and

•FOR the ratification of the appointment of EY.

The proxies will use their discretion with respect to voting on any other matters presented for a vote at the meeting. Additionally, if your proxy is executed and returned, it will be voted to approve the minutes of the 2024 Annual Meeting of Shareholders. This vote will not amount to a ratification of any action taken at that meeting nor will it indicate approval or disapproval of that action.

If your shares are registered in your name as the shareholder of record, you may vote by mail, telephone or Internet by following the instructions below. Voting instructions also appear on your proxy card. If you grant a proxy by telephone or by Internet, please have your proxy card available.

•To vote by mail, complete, sign, and return the enclosed proxy card in the postage paid envelope provided or return to: Vote Processing, c/o Broadridge, 51 Mercedes Way, Edgewood, New York, 11717.

•To vote by telephone, call toll free 1-800-690-6903 within the United States (“U.S.”), U.S. territories and Canada on a touch tone telephone by 11:59 p.m. eastern time on May 13, 2025. Have your proxy card in hand and follow the instructions.

•To vote by Internet, access the voting site at www.proxyvote.com. You will need the control number printed on your notice or proxy card.

The telephone and Internet voting procedures are designed to authenticate the shareholder's identity and to allow shareholders to vote their shares and confirm that their voting instructions have been properly recorded. Shareholders who vote by telephone or Internet do not need to return the proxy card.

If you hold your shares in “street name” in a stock brokerage account or through a bank, trust or other nominee, the broker or other nominee is considered the record holder and you are the beneficial owner of the shares. Beneficial owners vote their street name shares by instructing their broker or other nominee how to vote using the voting instruction form provided by the broker or nominee. Brokers only have authority to vote in their discretion on “routine” matters if they do not receive voting instructions from the beneficial owner of the shares.

Please note that the proposal to elect directors, the advisory vote on the compensation of the Company's named executive officers (the “Say-on-Pay” vote) and the approval of the 2025 Incentive Plan are not considered routine matters. Consequently, if you do not give your broker or nominee specific voting instructions with respect to such proposals, your street name shares will be treated as broker non-votes with respect to those proposals (see “Quorum, Voting Rights and Procedures” below) and will have no effect on the outcome of such proposals. The proposal to ratify the Audit Committee’s appointment of EY as the Company’s independent registered public accounting firm for the year ending December 31, 2025 is considered a routine matter.

If you hold your shares in street name and want to vote at the Annual Meeting, you must obtain from your broker or nominee a legal proxy issued in your name giving you the right to vote the shares directly at the meeting. You will not be entitled to vote at the meeting unless you present such a proxy to the Company at that time.