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• SOUTHSIDE BANCSHARES , INC . ANNOUNCES FINANCIAL RESULTS FOR THE FIRST QUARTER ENDED MARCH 31 , 2021 Record first quarter net income of $ 34.1 million , an increase of 762.4 % , compared to the same period in 2020 ; • Annualized return on first quarter average assets of 1.99 % ; • Annualized return on first quarter average tangible common equity of 21.22 % ( ¹ ) ; and • Nonperforming assets decreased to 0.22 % of total assets . EXHIBIT 99.1 Tyler , Texas ( April 23 , 2021 ) Southside Bancshares , Inc. ( " Southside " or the " Company " ) ( NASDAQ : SBSI ) today reported its financial results for the quarter ended March 31 , 2021. Southside reported net income of $ 34.1 million for the three months ended March 31 , 2021 , an increase of $ 30.1 million , or 762.4 % , compared to $ 4.0 million for the same period in 2020. Earnings per diluted common share increased $ 0.92 , or 766.7 % , to $ 1.04 for the three months ended March 31 , 2021 , from $ 0.12 for the same period in 2020. The annualized return on average shareholders ' equity for the three months ended March 31 , 2021 was 15.82 % , compared to 1.93 % for the same period in 2020. The annualized return on average assets was 1.99 % for the three months ended March 31 , 2021 , compared to 0.23 % for the same period in 2020 . " We reported outstanding results for the first quarter , highlighted by record net income , annualized linked quarter loan growth of 6.2 % , net of Paycheck Protection Program ( " PPP " ) loans , continued strong asset quality metrics and annualized linked quarter deposit growth of 13.2 % , " stated Lee R. Gibson , President and Chief Executive Officer of Southside . " Our record net income and earnings per diluted common share were primarily due to the $ 35.4 million decrease in provision for credit losses , from $ 25.2 million for the first quarter ended March 31 , 2020 , compared to a $ 10.1 million reversal of provision for the same period in 2021. This was largely due to our continued strong asset quality ratios , overall improvement in economic conditions , including lower unemployment levels , and a significant improvement in the economic forecast for March 2021 when compared to March 2020. " " We entered 2021 with an active loan pipeline , several of which closed and were funded during March , contributing to the 6.2 % first quarter annualized loan growth . We are encouraged about potential future loan growth as our pipeline continues to remain healthy . We have been actively participating in the second round of the PPP during 2021 , and as of April 21 , we have originated approximately 1,000 new loans totaling $ 105 million for small businesses in the market areas we serve . " " During February , Texas suffered a major power crisis due to the historic Winter Storm Uri , causing a massive electricity generation failure . This power crisis caused shortages of water , food and heat impacting large portions of the state . In addition , large accumulations of snow and ice created extremely hazardous driving conditions . Our technology facilities continued to operate uninterrupted with the use of backup power systems , allowing those team members with power , to work from home and handle virtually all customer transactions with the assistance of our ATM network for cash needs . Utilizing proven methods and technology , we were able to open the bank virtually until conditions improved with very few team members present and minimal customer inconvenience . " " Economic conditions in our market areas continue to improve , bolstered by company relocations and population growth due to individuals moving to Texas from other states . During the first quarter we hired additional revenue producers , one in Austin and two in the DFW area to generate additional loan growth . " Page - 1