Exhibit 99.1

FOR IMMEDIATE RELEASE

Prosperity Bancshares, Inc.^®

REPORTS FIRST QUARTER

2016 EARNINGS

HOUSTON, April 27, 2016. Prosperity Bancshares, Inc.^® (NYSE: PB), the parent company of Prosperity Bank^® (collectively, “Prosperity”), reported net income for the quarter ended March 31, 2016 of $68.951 million or $0.98 per diluted common share. Additionally, nonperforming assets remain low at 0.29% of first quarter average earning assets.

“I am pleased to share the positive earnings we showed for the first quarter of 2016. We showed an impressive return on first quarter average tangible common equity of 17.60% and a notable 1.24% annualized return on first quarter average assets. Our earnings were impacted by a larger than normal provision for credit losses of $14.0 million. During the quarter we experienced a loss in three credits that were from acquired banks. Two of the credits were energy credits with total charge-offs of $6.0 million and one was an agricultural credit with a charge-off of $7.0 million,” said David Zalman, Prosperity’s Chairman and Chief Executive Officer.

“Despite the downturn in the oil and gas industry, the unemployment rates in Texas and Oklahoma remain strong. Obviously, parts of Texas are impacted more than others, such as Midland/Odessa, South Texas and Houston; however, other parts of Texas and Oklahoma are doing well, including Dallas/Ft. Worth, which has shown solid population and job growth, as well as Austin, San Antonio and the Bryan/College Station area. The petrochemical, medical and hospitality industries have taken up a lot of slack in the Houston and South Texas areas. I am constantly amazed at the resiliency in the markets we serve. Grade A office space and apartments have been negatively impacted in Houston, but are still holding up fairly well. Retail real estate is continuing to do very well. The aerospace industry is creating new jobs and a need for new homes in Oklahoma,” continued Zalman.

“Our associates are working hard selling our products and services, including deposits, loans, trust, mortgage banking, wealth management and cash management, as well as others that help our customers with their financial stability. I am very optimistic about our future. We believe that the hard work of our entire team will help our customers grow and, in turn, increase shareholder value,” concluded Zalman.

Results of Operations for the Three Months Ended March 31, 2016

Net income was $68.951 million for the three months ended March 31, 2016 compared with $73.641 million for the same period in 2015. Net income per diluted common share was $0.98 for the three months ended March 31, 2016 compared with $1.05 for the same period in 2015. Net income (excluding purchase accounting adjustments) was $60.239 million for the quarter ended March 31, 2016 compared with $61.378 million for the quarter ended March 31, 2015. Net income per diluted common share (excluding purchase accounting adjustments) was $0.86 for the three months ended March 31, 2016 compared with $0.88 for the three months ended March 31, 2015. The reconciliation of these non-GAAP financial measures is shown on page 11. Annualized returns on average assets, average common equity and average tangible common equity for the three months ended March 31, 2016 were 1.24%, 7.85% and 17.60%, respectively. Prosperity’s efficiency ratio (excluding credit loss provisions, net gains and losses on the sale of assets and taxes) was 41.08% for the three months ended March 31, 2016.

Net interest income before provision for credit losses for the quarter ended March 31, 2016 was $166.257 million compared with $162.905 million during the same period in 2015. This increase was primarily due to an increase in average interest-earning assets of 3.8%, partially offset by a decrease in loan discount accretion of $5.153 million for the three months ended March 31, 2016. Linked quarter net interest income before provision for credit losses was $166.257 million compared with $153.258 million during the three months ended December 31, 2015, primarily due to the acquisition of Tradition Bancshares, Inc. and its wholly-owned subsidiary Tradition Bank (collectively “Tradition”) on January 1, 2016.

The net interest margin on a tax equivalent basis was 3.48% for the three months ended March 31, 2016, compared with 3.57% for the same period in 2015. This change was primarily due to a decrease in loan discount accretion of $5.153 million for the three months ended March 31, 2016 compared with the three months ended March 31, 2015. Linked quarter net interest margin on a tax equivalent basis was 3.48% for the three months ended March 31, 2016 compared with 3.24% for the three months ended December 31, 2015. This change was primarily due to an increase in average interest-earning assets and loan discount accretion. Excluding purchase accounting adjustments, the net interest margin on a tax equivalent basis was 3.21% for the three months ended March 31, 2016, compared with 3.17% for the same period in 2015 and 3.11% for the three months ended December 31, 2015. The reconciliation of these non-GAAP financial measures is shown on page 11.

Noninterest income was $30.793 million for the three months ended March 31, 2016 compared with $28.421 million for the same period in 2015, an increase of $2.372 million or 8.3%. This change was due to an increase in service charges on deposit accounts, an increase in mortgage income and an increase in other noninterest income. On a linked quarter basis, noninterest income increased $510 thousand or 1.7% compared with the quarter ended December 31, 2015.

Noninterest expense was $80.528 million for the three months ended March 31, 2016 compared with $79.462 million for the same period in 2015, an increase of $1.066 million or 1.3%. This change was primarily due to an increase in other noninterest expense. On a linked quarter basis, noninterest expense increased $2.619 million or 3.4% compared with the quarter ended December 31, 2015. This was primarily due to an increase in salaries and benefits expense as a result of the Tradition acquisition and an increase in regulatory assessments and FDIC insurance. One-time pre-tax merger related expenses of $624 thousand related to the Tradition acquisition were recorded during the first quarter of 2016.

Balance Sheet Information

At March 31, 2016, Prosperity had $21.978 billion in total assets, an increase of $371.486 million or 1.7%, compared with $21.607 billion at March 31, 2015.

Loans at March 31, 2016 were $9.654 billion, an increase of $488.403 million or 5.3%, compared with $9.166 billion at March 31, 2015. Linked quarter loans increased $215.819 million or 2.3% (9.1% annualized) from $9.439 billion at December 31, 2015. Linked quarter loans were impacted by the acquisition of Tradition and a reduction in oil and gas loans.

As part of its commercial and industrial lending activities, Prosperity extends credit to oil and gas production and service companies. Oil and gas production loans are loans to companies directly involved in the exploration and/or production of oil and gas. Oil and gas service loans are loans to companies that provide services for oil and gas production and exploration. At March 31, 2016, oil and gas loans totaled $362.826 million or 3.8% of total loans, of which $166.422 million were to production companies and $196.404 million were to service companies. This compares with total oil and gas loans of $461.838 million or 5.0% of total loans at March 31, 2015, of which $213.177 million were to production companies and $248.661 million were to service companies. On a linked quarter basis, oil and gas loans decreased $36.258 million, from $399.084 million or 4.2% of total loans at December 31, 2015, of which $178.614 million were production loans and $220.470 million were servicing loans.

Deposits at March 31, 2016 were $17.873 billion, an increase of $311.414 million or 1.8%, compared with $17.561 billion at March 31, 2015. Linked quarter deposits increased $191.647 million or 1.1% from $17.681 billion at December 31, 2015.

The table below provides detail on loans acquired and deposits assumed in the acquisition of Tradition completed on January 1, 2016:

Balance Sheet Data (at period end)

(In thousands)

Excluding loans acquired in the Tradition acquisition and new production at the acquired banking centers since the acquisition date, loans at March 31, 2016 increased $256.243 million or 2.8% compared with March 31, 2015 and, on a linked quarter basis, decreased $16.341 million or 0.2%.

Excluding deposits assumed in the Tradition acquisition and new deposits generated at the acquired banking centers since the acquisition date, deposits at March 31, 2016 decreased $164.789 million or 0.9% compared with March 31, 2015 and, on a linked quarter basis, decreased $284.556 million or 1.6%.

Asset Quality

Nonperforming assets totaled $56.985 million or 0.29% of quarterly average interest-earning assets at March 31, 2016, compared with $35.376 million or 0.19% of quarterly average interest-earning assets at March 31, 2015, and $43.459 million or 0.23% of quarterly average interest-earning assets at December 31, 2015. On a linked quarter basis, nonperforming assets increased $13.526 million or 31.1%. This increase was primarily due to an agricultural loan and other real estate acquired from Tradition.

The allowance for credit losses was 0.87% of total loans at March 31, 2016, 0.88% of total loans at March 31, 2015 and 0.86% of total loans at December 31, 2015. Excluding loans acquired that are accounted for under FASB Accounting Standards Codification (“ASC”) Topics 310-20 and 310-30, the allowance for credit losses was 1.03% of remaining loans as of March 31, 2016, compared with 1.12% at March 31, 2015 and 1.01% at December 31, 2015. Refer to the “Notes to Selected Financial Data” at the end of this Earnings Release for a reconciliation of this non-GAAP financial measure.

The provision for credit losses was $14.000 million for the three months ended March 31, 2016 compared with $1.250 million for the three months ended March 31, 2015 and $500 thousand for the three months ended December 31, 2015.

Net charge-offs were $11.670 million for the three months ended March 31, 2016 compared with $1.049 million for the three months ended March 31, 2015 and $119 thousand for the three months ended December 31, 2015. This increase was primarily due to charge-offs related to one agricultural loan and two energy loans during the first quarter of 2016.

Conference Call

Prosperity’s management team will host a conference call on Wednesday, April 27, 2016 at 10:30 a.m. Eastern Time (9:30 a.m. Central Time) to discuss Prosperity’s first quarter 2016 earnings. Individuals and investment professionals may participate in the call by dialing 877-883-0383. The elite entry number is 7806381.

Alternatively, individuals may listen to the live webcast of the presentation by visiting Prosperity’s website at www.prosperitybankusa.com. The webcast may be accessed directly from Prosperity’s home page by clicking the “Investor Relations” tab and then the “Presentations & Calls” link.

Non-GAAP Financial Measures

Prosperity’s management uses certain non−GAAP financial measures to evaluate its performance. Specifically, Prosperity reviews tangible book value per share, return on average tangible common equity and the tangible equity to tangible assets ratio. Further, as a result of acquisitions, and the related purchase accounting adjustments, Prosperity uses certain non-GAAP measures and ratios that exclude the impact of these items to evaluate its net income and earnings per share (excluding purchase accounting adjustments) and its allowance for credit losses to total loans (excluding acquired loans accounted for under ASC Topics 310-20, “Receivables-Nonrefundable Fees and Other Costs” and 310-30, “Receivables-Loans and Debt Securities Acquired with Deteriorated Credit Quality”). Prosperity has included in this Earnings Release information related to these non-GAAP financial measures for the applicable periods presented. Please refer to page 11 and to the “Notes to Selected Financial Data” at the end of this Earnings Release for a reconciliation of these non-GAAP financial measures.

Dividend

Prosperity Bancshares, Inc. (“Prosperity Bancshares”) declared a second quarter cash dividend of $0.30 per share, to be paid on July 1, 2016 to all shareholders of record as of June 17, 2016.

Stock Repurchase Program

On January 27, 2016, Prosperity Bancshares announced a stock repurchase program under which up to 5%, or approximately 3.54 million shares, of its outstanding common stock may be acquired over the next twelve months at the discretion of management.  During the first quarter of 2016, Prosperity Bancshares repurchased 1.16 million shares of its common stock at an average weighted price of $40.66 per share. 

Acquisition of Tradition Bancshares, Inc.

On January 1, 2016, Prosperity Bancshares completed the acquisition of Tradition Bancshares, Inc. and its wholly-owned subsidiary Tradition Bank headquartered in Houston, Texas. Tradition Bank operated 7 banking offices in the Houston, Texas area, including its main office in Bellaire, 3 banking centers in Katy and 1 banking center in The Woodlands. As of December 31, 2015, Tradition Bancshares, Inc., on a consolidated basis, reported total assets of $547.963 million, total loans of $253.315 million, total deposits of $488.928 million and shareholders’ equity of $43.103 million.

Under the terms of the definitive agreement, Prosperity Bancshares issued 679,528 shares of Prosperity Bancshares common stock plus $39.0 million in cash for all outstanding shares of Tradition Bancshares, Inc. capital stock.

Prosperity Bancshares, Inc. ^®

As of March 31, 2016, Prosperity Bancshares, Inc. ^® is a $21.978 billion Houston, Texas based regional financial holding company, formed in 1983. Operating under a community banking philosophy and seeking to develop broad customer relationships based on service and convenience, Prosperity offers a variety of traditional loan and deposit products to its customers, which consist primarily of small and medium sized businesses and consumers. In addition to established banking products, Prosperity offers a complete line of services including: Internet Banking services at www.prosperitybankusa.com, Retail Brokerage Services, Credit Cards, MasterMoney Debit Cards, 24 hour voice response banking, Trust and Wealth Management, Mortgage Services, Cash Management and Mobile Banking.

Prosperity currently operates 245 full-service banking locations: 65 in the Houston area, including The Woodlands; 29 in the South Texas area including Corpus Christi and Victoria; 36 in the Dallas/Fort Worth area; 22 in the East Texas area; 29 in the Central Texas area including Austin and San Antonio; 34 in the West Texas area including Lubbock, Midland-Odessa and Abilene; 16 in the Bryan/College Station area, 6 in the Central Oklahoma area and 8 in the Tulsa, Oklahoma area.

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“Safe Harbor” Statement under the Private Securities Litigation Reform Act of 1995: This release contains, and the remarks by Prosperity’s management on the conference call may contain, forward-looking statements within the meaning of the securities laws that are based on current expectations, assumptions, estimates and projections about Prosperity Bancshares and its subsidiaries. These forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties, many of which are outside of Prosperity’s control, which may cause actual results to differ materially from those expressed or implied by the forward-looking statements. These risks and uncertainties include but are not limited to whether Prosperity can: successfully identify acquisition targets and integrate the businesses of acquired companies and banks; continue to sustain its current internal growth rate or total growth rate; provide products and services that appeal to its customers; continue to have access to debt and equity capital markets; and achieve its sales objectives. Other risks include, but are not limited to: the possibility that credit quality could deteriorate; actions of competitors; changes in laws and regulations (including changes in governmental interpretations of regulations and changes in accounting standards); a deterioration or downgrade in the credit quality and credit agency ratings of the securities in Prosperity’s securities portfolio; customer and consumer demand, including customer and consumer response to marketing; effectiveness of spending, investments or programs; fluctuations in the cost and availability of supply chain resources; economic conditions, including currency rate, interest rate and commodity price fluctuations; and weather. These and various other factors are discussed in Prosperity Bancshares’ Annual Report on Form 10-K for the year ended December 31, 2015 and other reports and statements Prosperity Bancshares has filed with the SEC. Copies of the SEC filings for Prosperity Bancshares^® may be downloaded from the Internet at no charge from http://www.prosperitybankusa.com.

Prosperity Bancshares, Inc.^®

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Prosperity Bancshares, Inc.^®

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Prosperity Bancshares, Inc. ^®

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(Dollars and share amounts in thousands, except per share data and market prices)

Prosperity Bancshares, Inc.®

Financial Highlights (Unaudited)

(Dollars in thousands)

Prosperity Bancshares, Inc.®

Financial Highlights (Unaudited)

(Dollars in thousands, except per share data)