Exhibit 99.1

FOR IMMEDIATE RELEASE

PROSPERITY BANCSHARES, INC.^®

REPORTS FOURTH QUARTER

2017 EARNINGS

HOUSTON, January 24, 2018. Prosperity Bancshares, Inc.^® (NYSE: PB), the parent company of Prosperity Bank^® (collectively, “Prosperity”), reported net income for the quarter ended December 31, 2017 of $67.138 million or $0.97 per diluted common share. Additionally, nonperforming assets remain low at 0.19% of fourth quarter average interest-earning assets. As a result of the Tax Cuts and Jobs Act passed in December 2017, the Company was required to recalculate its deferred tax assets and deferred tax liabilities to account for the future impact of lower corporate tax rates and lost deductions on these assets and liabilities. The recalculation negatively impacted the Company’s fourth quarter 2017 net income in the amount of $1.431 million or $0.02 per diluted common share (“Tax Act Charge”), but the reduction in corporate tax rates is expected to positively impact net income in the future. Excluding the Tax Act Charge, net income and diluted earnings per share for the fourth quarter 2017 were $68.569 million and $0.99, respectively.

“Texas survived Hurricane Harvey and bounced back to robust growth of 2.6% - adding 286,000 jobs through November 2017.  The unemployment rate in Texas of 3.8% is the lowest since 1970 and higher oil prices continue to improve the energy sector,” said David Zalman, Prosperity’s Chairman and Chief Executive Officer.  

“Oklahoma’s economy experienced a solid recovery in 2017.  The state’s energy sector led the initial stages of recovery, but most other sectors also improved in 2017.  The outlook in Oklahoma for 2018 is positive,” added Zalman.

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“On December 22, 2017, the Tax Cuts and Jobs Act was enacted, which reduces the corporate tax rate from 35% to 21%.  The Act is expected to allow companies, such as Prosperity, to be more competitive, improve the lives of their employees and increase shareholder value,” stated Zalman.  

“At Prosperity, we communicate to our associates that they will be rewarded when the company does well.  Accordingly, given the expected positive financial impact of the lower tax rate, we are pleased to announce that we will provide the following to all associates at Prosperity Bank, other than the members of Prosperity Bank’s Executive Committee, whose compensation is reviewed and approved by Prosperity’s Compensation Committee:

We are excited that we are able to reward our associates for the many contributions they have made to Prosperity’s success,” continued Zalman.  

“Our customers are optimistic because of the reduced regulatory restrictions and the expected financial benefit from the reduced tax rates.  In the fourth quarter 2017, loans increased 4.4% annualized, and exceeded $10 billion for the first time in Prosperity’s history.  Deposits at December 31, 2017 increased $913.984 million or 5.4% from $16.907 billion at September 30, 2017,” added Zalman.

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

Results of Operations for the Three Months Ended December 31, 2017

Net income was $67.138 million⁽²⁾ for the three months ended December 31, 2017 compared with $68.793 million⁽³⁾ for the same period in 2016. Net income per diluted common share was $0.97 for the three months ended December 31, 2017 compared with $0.99 for the same period in 2016. Net income and earnings per diluted common share for the three months ended December 31, 2017 were impacted by the one-time non-cash Tax Act Charge of $1.431 million or $0.02 per diluted common share. Excluding the Tax Act Charge, net income and earnings per diluted common share for the three months ended December 31, 2017 were $68.569 million and $0.99, respectively. Annualized returns on average assets, average common equity and average tangible common equity for the three months ended December 31, 2017 were 1.20%, 7.04% and 14.31%⁽¹⁾, respectively.  Excluding the Tax Act Charge, annualized returns on average assets, average common equity and average tangible common equity for the three months ended December 31, 2017 were 1.23%, 7.19% and 14.62%, respectively. Prosperity’s efficiency ratio (excluding credit loss provisions, net gains and losses on the sale of assets and taxes) was 43.78%⁽¹⁾ for the three months ended December 31, 2017.

Net interest income before provision for credit losses for the three months ended December 31, 2017 was $156.050 million compared with $153.832 million during the same period in 2016, an increase of $2.218 million or 1.4%. This change was primarily due to an increase in the average balance and yield on interest-earning assets, partially offset by an increase in the average rate on interest-bearing liabilities. Linked quarter net interest income before provision for credit losses decreased $97 thousand or 0.1% to $156.050 million compared with $156.147 million during the three months ended September 30, 2017. This decrease was primarily due to a decrease in loan discount accretion of $3.090 million.

The net interest margin on a tax equivalent basis was 3.20% for the three months ended December 31, 2017 compared with 3.26% for the same period in 2016. This change was primarily due to a decrease in loan discount accretion of $2.756 million. On a linked quarter basis, the net interest margin was 3.20% compared with 3.22% for the three months ended September 30, 2017. This decrease was primarily due to a decrease in loan discount accretion of $3.090 million.

Noninterest income was $29.220 million for the three months ended December 31, 2017 compared with $29.475 million for the same period in 2016, a decrease of $255 thousand or 0.9%. This change was primarily due to a decrease in mortgage income. On a linked quarter basis, noninterest income increased $411 thousand or 1.4% compared with the three months ended September 30, 2017.

Noninterest expense was $81.088 million for the three months ended December 31, 2017 compared with $79.148 million for the same period in 2016, an increase of $1.940 million or 2.5%. This change was primarily due to the write-down of other real estate, partially offset by a decrease in salaries and benefits. On a linked quarter basis, noninterest expense increased $3.579 million or 4.6% compared with the three months ended September 30, 2017. This increase was primarily due to the write-down of other real estate.

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Results of Operations for the Year Ended December 31, 2017

Net income was $272.165 million⁽⁴⁾ for the year ended December 31, 2017 compared with $274.466 million⁽⁵⁾ for the same period in 2016.  Net income per diluted common share was $3.92 for the year ended December 31, 2017 compared with $3.94 for the same period in 2016. Annualized returns on average assets, average common equity and average tangible common equity for the year ended December 31, 2017 were 1.22%, 7.26% and 15.06%⁽¹⁾, respectively.  Prosperity’s efficiency ratio (excluding credit loss provisions, net gains and losses on the sale of assets and securities and taxes) was 42.76%⁽¹⁾ for the year ended December 31, 2017.

Net interest income before provision for credit losses for the year ended December 31, 2017 was $616.863 million compared with $632.620 million for the same period in 2016, a decrease of $15.757 million or 2.5%. This change was primarily due to a decrease in loan discount accretion of $17.064 million and an increase in the average rate on interest-bearing liabilities, partially offset by an increase in average interest-earnings assets.

The net interest margin on a tax equivalent basis for the year ended December 31, 2017 was 3.19% compared with 3.35% for the same period in 2016. This change was primarily due to a decrease in loan discount accretion of $17.064 million and an increase in the average rate on interest-bearing liabilities.

Noninterest income was $116.633 million for the year ended December 31, 2017 compared with $118.425 million for the same period in 2016, a decrease of $1.792 million or 1.5%. This change was primarily due to the net loss on sale of assets and a decrease in brokerage and mortgage income, partially offset by a gain on sale of securities and an increase in service charges on deposit accounts.

Noninterest expense was $313.101 million for the year ended December 31, 2017 compared with $318.387 million for the same period in 2016, a decrease of $5.286 million or 1.7%.  This change was primarily due to a decrease in salaries and benefits and core deposit intangibles amortization, partially offset by the write-down of other real estate.

Balance Sheet Information

At December 31, 2017, Prosperity had $22.587 billion in total assets, an increase of $256.220 million or 1.1%, compared with $22.331 billion at December 31, 2016.

Loans at December 31, 2017 were $10.021 billion, an increase of $398.713 million or 4.1%, compared with $9.622 billion at December 31, 2016. Linked quarter loans increased $109.571 million or 1.1% (4.4% annualized) from $9.911 billion at September 30, 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 December 31, 2017, oil and gas loans totaled $300.546 million or 3.0% of total loans, of which $112.246 million were to production companies and $188.300 million were to service companies. This compares with total oil and gas loans of $284.539 million or 3.0% of total loans at December 31, 2016, of which $119.934 million were to production companies and $164.605 million were to service companies. At September 30, 2017, oil and gas loans totaled $291.827 million or 2.9% of total loans, of which $106.524 million were production loans and $185.303 million were service loans.

Deposits at December 31, 2017 were $17.821 billion, an increase of $514.158 million or 3.0%, compared with $17.307 billion at December 31, 2016. Linked quarter deposits increased $913.984 million or 5.4% from $16.907 billion at September 30, 2017.

Asset Quality

Nonperforming assets totaled $37.455 million or 0.19% of quarterly average interest-earning assets at December 31, 2017, compared with $48.302 million or 0.25% of quarterly average interest-earning assets at December 31, 2016, and $45.823 million or 0.24% of quarterly average interest-earning assets at September 30, 2017.

The allowance for credit losses was $84.041 million or 0.84% of total loans at December 31, 2017, $85.326 million or 0.89% of total loans at December 31, 2016 and $86.812 million or 0.88% of total loans at September 30, 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 0.91%⁽¹⁾ of remaining loans as of December 31, 2017, compared with 1.00%⁽¹⁾ at December 31, 2016 and 0.95%⁽¹⁾ at September 30, 2017.

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The provision for credit losses was $2.000 million for the three months ended December 31, 2017 compared with $2.000 million for the three months ended December 31, 2016 and $6.900 million for the three months ended September 30, 2017.  The provision for credit losses was $14.325 million for the year ended December 31, 2017 compared with $24.000 million for the year ended December 31, 2016.

Net charge-offs were $4.771 million for the three months ended December 31, 2017 compared with $2.259 million for the three months ended December 31, 2016 and $3.871 million for the three months ended September 30, 2017. Net charge-offs for the fourth quarter of 2017 were primarily comprised of two commercial and industrial loans.  Net charge-offs were $15.610 million for the year ended December 31, 2017 compared with $20.058 million for the year ended December 31, 2016.

Dividend

Prosperity Bancshares, Inc. declared a first quarter cash dividend of $0.36 per share to be paid on April 2, 2018 to all shareholders of record as of March 16, 2018.

Conference Call

Prosperity’s management team will host a conference call on Wednesday, January 24, 2018 at 11:00 a.m. Eastern Time (10:00 a.m. Central Time) to discuss Prosperity’s fourth quarter 2017 earnings. Individuals and investment professionals may participate in the call by dialing 877-883-0383. The elite entry number is 5067257.

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 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 December 31, 2017, Prosperity Bancshares, Inc. ^® is a $22.587 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.

As of December 31, 2017, 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.

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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. 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, 2016 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 ($143), $1,635, $2,871, $2,200 and $2,171 in unrealized (losses) gains on available for sale securities for the quarterly periods ended December 31, 2017, September 30, 2017, June 30, 2017, March 31, 2017 and December 31, 2016, respectively.

(B) Includes ($113), $1,063, $1,866, $1,430 and $1,411 in after-tax unrealized (losses) gains on available for sale securities for the quarterly periods ended December 31, 2017, September 30, 2017, June 30, 2017, March 31, 2017 and December 31, 2016, 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 $9,521, $10,115, $9,403, $9,883 and $11,502 for the three-month periods ended December 31, 2017, September 30, 2017, June 30, 2017, March 31, 2017 and December 31, 2016, respectively, and $38,922 and $43,474 for the years ended December 31, 2017 and December 31, 2016, 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 34.3%, 32.5%, 32.0%, 33.1% and 32.7% for the three-month periods ended December 31, 2017, September 30, 2017,  June 30, 2017, March 31, 2017 and December 31, 2016, respectively, and 33.0% and 32.8% for the years ended December 31, 2017 and December 31, 2016, 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 or 366 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)