S&T Bancorp (STBA) 10-K 2021 FY Annual report

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the following Registration Statements:

1.Registration Statement (Form S-3 No. 333-258470) of S&T Bancorp, Inc. pertaining to the automatic shelf     registration filed August 5, 2021,

2.Registration Statement (Form S-3 No. 333-156555) of S&T Bancorp, Inc. pertaining to the Dividend Reinvestment and Stock Purchase Plan,

3.Registration Statement (Form S-8 No. 333-194083) of S&T Bancorp, Inc. pertaining to the 2014 Incentive Plan filed on February 21, 2014,

4.Registration Statement (Form S-8 No. 333- 258482) of S&T Bancorp, Inc. pertaining to the 2021 Incentive Plan filed on August 5, 2021, and

5.Registration Statement (Form S-8 No. 333-156541) of S&T Bancorp, Inc. pertaining to the Thrift Plan for Employees of S&T Bank;

of our reports dated February 28, 2022, with respect to the consolidated financial statements of S&T Bancorp, Inc. and the effectiveness of internal control over financial reporting of S&T Bancorp, Inc. included in this Annual Report (Form 10-K) of S&T Bancorp, Inc. for the year ended December 31, 2021.

/s/ Ernst & Young LLP

Pittsburgh, Pennsylvania

February 28, 2022