Exhibit 99.1

FOR IMMEDIATE RELEASE

PROSPERITY BANCSHARES, INC.^®

REPORTS FIRST QUARTER

2018 EARNINGS

HOUSTON, April 25, 2018. Prosperity Bancshares, Inc.^® (NYSE: PB), the parent company of Prosperity Bank^® (collectively, “Prosperity”), reported net income for the quarter ended March 31, 2018 of $74.361 million or $1.07 per diluted common share. Additionally, nonperforming assets remain low at 0.17% of first quarter average interest-earning assets.

“The Texas and Oklahoma economies continue to grow helped by the diversity of business, low or no state income tax, a business friendly climate and a strong tailwind from an improving energy industry.  The Dallas Federal Reserve Bank is projecting 3.4% job growth for Texas in 2018, or 418,000 new jobs.  Houston is making a comeback with 4.7% annualized job growth through February 2018, an expected 160,000 new jobs. Oklahoma’s unemployment rate in February 2018 was 4.1% and remains unchanged since September 2017.  Employment growth has added jobs across most industries,” said David Zalman, Prosperity’s Chairman and Chief Executive Officer.

“We were excited to see earnings per share for the first quarter of 2018 increase 8.1% compared with the first quarter of 2017, first quarter net income increase 10.7% to $74.361 million compared with the fourth quarter of 2017 of $67.138 million and a return on tangible capital of 15.43%.  Despite the increase, earnings should have been better.  Net charge-offs for the quarter of $9.441 million were an anomaly.  Approximately two-thirds of this amount were previously identified problem credits inherited from our last acquisition in Oklahoma.  The charge-offs related to these credits represented a loss of seven cents per share. While disappointing, with respect to the largest charge-off, rather than continue to carry the problem asset for an unpredictable future period, we elected to accept a discounted offer and reduce our nonperforming assets,” continued Zalman.  

“Loans at March 31, 2018 were $10.011 billion, an increase of $272.163 million or 2.8%, compared with $9.739 billion at March 31, 2017, and essentially flat compared with the fourth quarter of 2017.  We experienced a number of large pay downs in the quarter that impacted our overall growth.  However, the good news is that loan production was strong and given the expected funding of these new loans, we believe that we will achieve the 2018 organic loan growth guidance we gave earlier this year,” added Zalman.

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“We remain excited about 2018.  Although we have had large loan pay downs due to our customers selling their projects, converting completed projects to long term financing or using cash reserves to pay down debt because of more economic certainty, we believe that this increased certainty should result in businesses and individuals taking calculated risks and needing loan funding to do so,” stated Zalman.

“I would like to thank all of our customers, associates, directors and shareholders for helping make such a successful Bank.  Prosperity Bank was rated by Forbes as one of the Best Banks In America again for 2018.  Prosperity is the only Texas-based bank in the Top 10, and we have been in the Top 10 and the highest rated Texas-based bank for five consecutive years,” concluded Zalman.

Results of Operations for the Three Months Ended March 31, 2018

Net income was $74.361 million⁽²⁾ for the three months ended March 31, 2018 compared with $68.565 million⁽³⁾ for the same period in 2017, an increase of $5.796 million or 8.5%. Net income per diluted common share was $1.07 for the three months ended March 31, 2018 compared with $0.99 for the same period in 2017, an increase of 8.1%. Net income and earnings per diluted common share for the three months ended March 31, 2018 reflect the reduction in corporate tax rate from 35% to 21% as a result of the Tax Cuts and Jobs Act of 2017. Additionally, net income and earnings per diluted common share were impacted by higher than normal net charge-offs of $9.441 million. Annualized returns on average assets, average common equity and average tangible common equity for the three months ended March 31, 2018 were 1.32%, 7.69% and 15.43%⁽¹⁾, respectively.  Prosperity’s efficiency ratio (excluding credit loss provisions and taxes) was 44.19%⁽¹⁾ for the three months ended March 31, 2018.

Net interest income before provision for credit losses for the three months ended March 31, 2018 was $153.223 million compared with $152.435 million during the same period in 2017, an increase of $788 thousand or 0.5%. This change was primarily due to an increase in income on loans, partially offset by an increase in the average rate on interest bearing deposits and a decrease in loan discount accretion. Linked quarter net interest income before provision for credit losses decreased $2.827 million or 1.8% to $153.223 million compared with $156.050 million during the three months ended December 31, 2017. This decrease was primarily due to an increase in the average rate on interest bearing deposits and a decrease in loan discount accretion.

The net interest margin on a tax equivalent basis was 3.16% for the three months ended March 31, 2018 compared with 3.20% for the same period in 2017 and for the three months ended December 31, 2017. The change during both periods was primarily due to a decrease in loan discount accretion.

Noninterest income was $27.938 million for the three months ended March 31, 2018 compared with $30.824 million for the same period in 2017, a decrease of $2.886 million or 9.4%. This change was primarily due to the net gain on sale of assets during the first quarter of 2017. On a linked quarter basis, noninterest income decreased $1.282 million or 4.4% primarily due to decreases in NSF fees and credit/debit card income.

Noninterest expense was $80.054 million for the three months ended March 31, 2018 compared with $78.062 million for the same period in 2017, an increase of $1.992 million or 2.6%. This change was primarily due to an increase in salaries and benefits. On a linked quarter basis, noninterest expense decreased $1.034 million or 1.3% compared with the three months ended December 31, 2017. This change primarily resulted from a write-down of other real estate of $3.380 million during the fourth quarter of 2017, partially offset by an increase in salaries and benefits.

Balance Sheet Information

At March 31, 2018, Prosperity had $22.472 billion in total assets compared with $22.477 billion at March 31, 2017.

Loans at March 31, 2018 were $10.011 billion, an increase of $272.163 million or 2.8%, compared with $9.739 billion at March 31, 2017. Linked quarter loans decreased $9.357 million or 0.1% from $10.021 billion at December 31, 2017.

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, 2018, oil and gas loans totaled $375.405 million or 3.7% of total loans, of which $168.883 million were to production companies and $206.522 million were to service companies. This compares with total oil and gas loans of $267.445 million or 2.8% of total loans at March 31, 2017, of which $108.267 million were to production companies and $159.178 million were to service companies. At December 31, 2017, oil and gas loans totaled $300.546 million or 3.0% of total loans, of which $112.246 million were production loans and $188.300 million were service loans.

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Deposits at March 31, 2018 were $17.333 billion, an increase of $297.307 million or 1.7%, compared with $17.036 billion at March 31, 2017. Linked quarter deposits decreased $488.581 million or 2.7% from $17.821 billion at December 31, 2017. This change was primarily due to seasonality.

Asset Quality

Nonperforming assets totaled $33.217 million or 0.17% of quarterly average interest-earning assets at March 31, 2018, compared with $41.199 million or 0.21% of quarterly average interest-earning assets at March 31, 2017, and $37.455 million or 0.19% of quarterly average interest-earning assets at December 31, 2017.

The allowance for credit losses was $83.600 million or 0.84% of total loans at March 31, 2018, $84.095 million or 0.86% of total loans at March 31, 2017 and $84.041 million or 0.84% of total loans at December 31, 2017.  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 0.90%⁽¹⁾ of remaining loans as of March 31, 2018, compared with 0.96%⁽¹⁾ at March 31, 2017 and 0.91%⁽¹⁾ at December 31, 2017.

The provision for credit losses was $9.000 million for the three months ended March 31, 2018 compared with $2.675 million for the three months ended March 31, 2017 and $2.000 million for the three months ended December 31, 2017.  

Net charge-offs were $9.441 million for the three months ended March 31, 2018 compared with $3.906 million for the three months ended March 31, 2017 and $4.771 million for the three months ended December 31, 2017. Net charge-offs for the first quarter of 2018 were primarily comprised of three commercial and industrial loans, two of which were energy related.  

Dividend

Prosperity Bancshares, Inc. declared a second quarter cash dividend of $0.36 per share to be paid on July 2, 2018 to all shareholders of record as of June 15, 2018.

Conference Call

Prosperity’s management team will host a conference call on Wednesday, April 25, 2018 at 11:00 a.m. Eastern Time (10:00 a.m. Central Time) to discuss Prosperity’s first quarter 2018 earnings. Individuals and investment professionals may participate in the call by dialing 877-883-0383. The elite entry number is 3655171.

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 from Prosperity’s home page by selecting “Presentations & Calls” from the drop-down menu on the Investor Relations tab and following the instructions.

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, tangible equity to tangible assets ratio and the efficiency ratio, excluding net gains and losses on the sale of assets and securities.  Further, as a result of acquisitions and the related purchase accounting adjustments, Prosperity uses certain non-GAAP financial measures and ratios that exclude the impact of these items to evaluate 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 believes these non-GAAP financial measures provide information useful to investors in understanding Prosperity’s financial results and that their presentation, together with the accompanying reconciliations, provides a more complete understanding of factors and trends affecting Prosperity’s business and allows investors to view performance in a manner similar to management, the entire financial services sector, bank stock analysts and bank regulators. Further, Prosperity believes that these non-GAAP financial measures provide useful information by excluding certain items that may not be indicative of its core operating earnings and business outlook.  These non-GAAP financial measures should not be considered a substitute for, nor of greater importance than, GAAP basis measures and results; Prosperity strongly encourages investors to review its consolidated financial statements in their entirety and not to rely on any single financial measure. Because non-GAAP financial measures are not standardized, it may not be possible to compare these financial measures with other companies’ non-GAAP financial measures having the same or similar names. Please refer to the “Notes to Selected Financial Data” at the end of this Earnings Release for a reconciliation of these non-GAAP financial measures to the nearest respective GAAP financial measures.

Prosperity Bancshares, Inc. ®

As of March 31, 2018, Prosperity Bancshares, Inc. ^® is a $22.472 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

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Debit Cards, 24 hour voice response banking, Trust and Wealth Management, Mortgage Services, Cash Management and Mobile Banking.

As of March 31, 2018, Prosperity operated 242 full-service banking locations: 65 in the Houston area, including The Woodlands; 29 in the South Texas area including Corpus Christi and Victoria; 33 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.

“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. Forward-looking statements include all statements other than statements of historical fact, including forecasts or trends, and 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, 2017 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.

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Prosperity Bancshares, Inc.^®

Financial Highlights (Unaudited)

(In thousands)

(A) Includes $57, ($143), $1,635, $2,871 and $2,200 in unrealized gains (losses) on available for sale securities for the quarterly periods ended March 31, 2018, December 31, 2017, September 30, 2017, June 30, 2017 and March 31, 2017, respectively.

(B) Includes $45, ($113), $1,063, $1,866 and $1,430 in after-tax unrealized gains (losses) on available for sale securities for the quarterly periods ended March 31, 2018, December 31, 2017, September 30, 2017, June 30, 2017 and March 31, 2017, respectively.

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Prosperity Bancshares, Inc.^®

Financial Highlights (Unaudited)

(In thousands)

(C) Interest income on securities was reduced by net premium amortization of $8,450, $9,521, $10,115, $9,403 and $9,883 for the three-month periods ended March 31, 2018, December 31, 2017, September 30, 2017, June 30, 2017 and March 31, 2017, respectively.

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Prosperity Bancshares, Inc. ^®

Financial Highlights (Unaudited)

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

(D) Includes purchase accounting adjustments for the periods presented as follows:

(E) Using effective tax rate of 19.3%, 34.3%, 32.5%, 32.0% and 33.1% for the three-month periods ended March 31, 2018, December 31, 2017, September 30, 2017,  June 30, 2017 and March 31, 2017, respectively.

(F) Interim periods annualized.

(G) Refer to the "Notes to Selected Financial Data" at the end of this Earnings Release for a reconciliation of this non-GAAP financial measure.

(H) Net interest margin for all periods presented is based on average balances on an actual 365 day basis.

(I) Calculated by dividing total noninterest expense, excluding credit loss provisions, by net interest income plus noninterest income, excluding net gains and losses on the sale of assets and securities.  Additionally, taxes are not part of this calculation.

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Prosperity Bancshares, Inc.^®

Financial Highlights (Unaudited)

(Dollars in thousands)