Exhibit 99.1

S&T Bancorp, Inc. Announces Third Quarter

Earnings and Declares an Increased Dividend

Indiana, Pennsylvania – October 29, 2013 – S&T Bancorp, Inc. (S&T) (NASDAQ: STBA) has announced its third quarter earnings. Net income for the third quarter of 2013 was $12.2 million, or $0.41 per diluted share, compared to the second quarter of 2013 net income of $14.1 million, or $0.47 per diluted share, and the third quarter of 2012 net income of $12.6 million, or $0.43 per diluted share.

Third Quarter Highlights

“Our quarterly results reflect another strong quarter of performance with solid loan growth, continued asset quality improvement and an increase in net interest income,” said Todd Brice, president and chief executive officer of S&T. “We are also pleased to announce the increase in our quarterly cash dividend which is a reflection of S&T’s strong earnings and capital position.”

- more -

S&T Earnings Release –2

S&T Bancorp, Inc. Announces Third Quarter

Earnings and Declares an Increased Dividend

(continued)

Net Interest Income

Net interest income increased $0.7 million, or 2.0%, to $35.3 million compared to $34.6 million in the prior quarter. Net interest margin on a fully taxable equivalent basis (FTE) decreased one basis point to 3.50% compared to 3.51% in the second quarter of 2013. Both net interest income and net interest margin (FTE) were positively impacted by an improvement in funding costs during the third quarter of 2013. The improvement in funding costs was primarily due to the repayment of $45.0 million of subordinated debt late in the second quarter of 2013 which was replaced with lower costing short-term borrowings. Additionally, maturities of higher costing certificates of deposits shifted to lower costing deposits. Interest income remained unchanged as the positive impact from a $50.8 million increase in average earning assets was offset by a decrease in the earning asset rate of 7 basis points to 3.82% compared to 3.89% in the prior quarter.

Asset Quality

Asset quality continues to improve. Total nonperforming loans (NPLs) were $36.4 million, or 1.04%, of total loans at September 30, 2013, which represents a 3.9% decrease from $37.9 million, or 1.10%, of total loans at June 30, 2013. Special mention and substandard loans also decreased $46.4 million, or 17%, to $222.3 million from $268.7 million at June 30, 2013. Net charge-offs for the third quarter of 2013 were $1.5 million compared to net charge-offs of $0.9 million in the second quarter of 2013. The provision for loan losses was $3.4 million in the third quarter of 2013 compared to $1.0 million in the second quarter of 2013 primarily due to an increase of $3.1 million in specific reserves. The allowance for loan losses (ALL) increased slightly to $48.0 million, or 1.37% of total loans, compared to $46.1 million, or 1.34% of total loans, at June 30, 2013.

- more -

S&T Earnings Release –3

S&T Bancorp, Inc. Announces Third Quarter

Earnings and Declares an Increased Dividend

(continued)

Noninterest Income and Expense

Noninterest income decreased $0.4 million to $12.5 million compared to $12.9 million in the second quarter of 2013. Mortgage banking income decreased $0.6 million primarily due to the increase in interest rates that occurred in the second quarter of 2013. Debit and credit card fees decreased $0.4 million due to a decrease in merchant revenue. Service charges on deposit accounts increased $0.3 million due to changes in certain deposits fees implemented late in the second quarter of 2013. Other income increased $0.4 million primarily related to interest rate swap fees from our commercial customers.

Noninterest expense decreased $0.4 million, or 1.6%, to $27.9 million compared to $28.4 million in the second quarter of 2013. There were no significant changes to expense categories from the prior quarter. The third quarter results reflect the benefit of expense control initiatives implemented in the first half of 2013.

Financial Condition

Total assets increased to $4.6 billion at September 30, 2013 compared to $4.5 billion at June 30, 2013 and $4.4 billion at September 30, 2012. Loan growth was strong during the quarter with an increase of $68.1 million, or 2.0%, in total portfolio loans. Commercial loans grew $52.3 million, or 2.1%, during the quarter, due to strong growth in the commercial real estate portfolio. Consumer loans increased $15.8 million during the quarter with the majority of the growth in residential mortgages of $13.7 million, or 3.0%. Total deposit balances increased $45.6 million, or 1.2%, compared to June 30, 2013. The deposit mix improved with an increase in demand deposit accounts of $53.8 million, or 4.3%, from June 30, 2013. S&T’s risk-based capital ratios are down slightly this quarter as loan and commitment growth outpaced increased capital from retained earnings. All capital ratios remain significantly above the well-capitalized thresholds of federal bank regulatory agencies.

- more -

S&T Earnings Release –4

S&T Bancorp, Inc. Announces Third Quarter

Earnings and Declares an Increased Dividend

(continued)

Dividend

The Board of Directors of S&T declared a $0.16 per share cash dividend at its regular meeting held October 28, 2013, representing a 6.7% increase over the prior quarter cash dividend of $0.15 per share. The dividend is payable on November 29, 2013 to shareholders of record on November 15, 2013.

Conference Call

S&T will host its third quarter 2013 earnings conference call live over the Internet at 1:00 p.m. ET on Tuesday, October 29, 2013. To access the webcast, go to S&T’s webpage at www.stbancorp.com and click on “Events & Presentations.” Select “3rd Quarter 2013 Conference Call” and follow the instructions.

About S&T Bancorp, Inc.

Headquartered in Indiana, PA, S&T operates offices within Allegheny, Armstrong, Blair, Butler, Cambria, Clarion, Clearfield, Indiana, Jefferson, Washington and Westmoreland counties as well as a loan production office in northeast Ohio. With assets of $4.6 billion, S&T stock trades on the NASDAQ Global Select Market System under the symbol STBA. For more information, visit www.stbancorp.com.

This information may contain forward-looking statements regarding future financial performance which are not historical facts and which involve risks and uncertainties. Actual results and performance could differ materially from those anticipated by these forward-looking statements. Factors that could cause such a difference include, but are not limited to, general economic conditions, change in interest rates, deposit flows, loan demand, and asset quality, including real estate and other collateral values and competition. In addition to the results of operations presented in accordance with Generally Accepted Accounting Principles (GAAP), S&T management uses and this press release contains or references, certain non-GAAP financial measures, such as net interest income on a fully taxable equivalent basis. S&T believes these non-GAAP financial measures provide information useful to investors in understanding our underlying operational performance and our business and performance trends as they facilitate comparisons with the performance of others in the financial services industry. Although S&T believes that these non-GAAP financial measures enhance investors’ understanding of S&T’s business and performance, these non-GAAP financial measures should not be considered an alternative to GAAP. A reconciliation of these non-GAAP

- more -

S&T Earnings Release –5

S&T Bancorp, Inc. Announces Third Quarter

Earnings and Declares an Increased Dividend

(continued)

financial measures is presented in the attached selected financial data spreadsheet. This information should be read in conjunction with the audited financial statements and analysis as presented in the Annual Report on Form 10-K for S&T Bancorp, Inc. and subsidiaries.

- more -