S&T BANCORP INC

NOTE 1. BASIS OF PRESENTATION

Principles of Consolidation

The interim Condensed Consolidated Financial Statements include the accounts of S&T Bancorp, Inc., or S&T, and its wholly owned subsidiaries. All significant intercompany transactions have been eliminated in consolidation. Investments of 20 percent to 50 percent of the outstanding common stock of investees are accounted for using the equity method of accounting.

Basis of Presentation

The accompanying unaudited interim Condensed Consolidated Financial Statements of S&T have been prepared in accordance with generally accepted accounting principles, or GAAP, in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the audited Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025, or 2025 Form 10-K, filed with the Securities and Exchange Commission, or SEC. In the opinion of management, the accompanying interim financial information reflects all adjustments, consisting of normal recurring adjustments, necessary to present fairly our financial position and the results of operations for each of the interim periods presented. Results of operations for interim periods are not necessarily indicative of the results of operations that may be expected for a full year or any future period.

Reclassification

Amounts in prior period financial statements and footnotes are reclassified whenever necessary to conform to the current period presentation. Reclassifications had no effect on our condensed consolidated financial statements.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.

Segments

We haveone operating segment, Community Banking, based upon our current reporting structure at the consolidated level. The chief operating decision maker, or CODM, uses consolidated net income when allocating resources and making operating decisions. The accounting policies used to measure the profit and loss of the Community Banking segment are the same as those described in the summary of significant accounting policies in our 2025 Form 10-K. The CODM does not review segment revenue or expense information at a lower level than what is included in our Condensed Consolidated Statements of Comprehensive Income. Expenses included within other expenses in the Condensed Consolidated Statements of Comprehensive Income include loan related expenses, travel and entertainment, contributions and insurance expenses.

Recently Adopted Accounting Standards Updates, or ASUs

There were no recently adopted accounting standards updates in the third quarter of 2026.

Recently Issued Accounting Standards Not Yet Adopted

Income Statement (Subtopic 220-40)—Reporting Comprehensive Income—Expense Disaggregation Disclosures

In November 2024, the FASB issued ASU 2024-03, Income Statement (Subtopic 220-40)—Reporting Comprehensive Income—Expense Disaggregation Disclosures to improve the disclosures about a public business entity’s expenses and address requests from investors for more detailed information about the types of expenses in commonly presented expense captions. The amendments in this update are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. This ASU will not impact our consolidated financial statements and we are currently evaluating the impact of the new disclosure requirements.

Interim Reporting (Topic 270)—Narrow-Scope Improvements

In December 2025, the FASB issued ASU 2025-11, Interim Reporting (Topic 270)—Narrow-Scope Improvements to improve the navigability of the required interim disclosures and clarify when the guidance is applicable. The amendments also provide additional guidance on what disclosures should be provided in interim reporting periods. The amendments add to Topic 270 a principle that requires entities to disclose events since the end of the last annual reporting period that have a material impact on the entity. The amendments in this update are effective for annual reporting periods beginning after December 15, 2027, and interim reporting periods beginning after December 15, 2028. Early adoption is permitted. This ASU is not expected to have a material impact on disclosures.

NOTE 2. EARNINGS PER SHARE

The treasury stock method was used to determine earnings per share for the three and nine months ended September 30, 2026 and 2025. The following table reconciles the numerators and denominators of basic and diluted EPS calculations for the periods presented:

NOTE 3. FAIR VALUE MEASUREMENTS

We use fair value measurements when recording and disclosing certain financial assets and liabilities. Debt securities, equity securities, securities held in a deferred compensation plan and derivative financial instruments are recorded at fair value on a recurring basis. Additionally, from time to time, we may be required to record other financial instruments at fair value on a nonrecurring basis, such as loans held for sale, loans individually evaluated, other real estate owned, or OREO, and other repossessed assets, mortgage servicing rights, or MSRs, and certain other assets.

Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. An orderly transaction is a transaction that assumes exposure to the market for a period prior to the measurement date to allow for marketing activities that are usual and customary for transactions involving such assets or liabilities; it is not a forced transaction. In determining fair value, we use various valuation approaches, including market, income and cost approaches. The fair value standard establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability which are developed based on market data that we have obtained from independent sources. Unobservable inputs reflect our estimates of assumptions that market participants would use in pricing an asset or liability which are developed based on the best information available in the circumstances.

The fair value hierarchy gives the highest priority to unadjusted quoted market prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement). The fair value hierarchy is broken down into three levels based on the reliability of inputs as follows.

Level 1: valuation is based upon unadjusted quoted market prices for identical instruments traded in active markets.

Level 2: valuation is based upon quoted market prices for similar instruments traded in active markets, quoted market prices for identical or similar instruments traded in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by market data.

Level 3: valuation is derived from other valuation methodologies, including discounted cash flow models and similar techniques that use significant assumptions not observable in the market. These unobservable assumptions reflect estimates of assumptions that market participants would use in determining fair value.

A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.

There have been no changes in our valuation methodologies during the three and nine months ended September 30, 2026. Refer to Note 1. Summary of Significant Accounting Policies of the Notes to Consolidated Financial Statements in our 2025 Form 10-K for more information on the valuation methodologies that we use for financial instruments recorded at fair value on a recurring or nonrecurring basis.

Assets and Liabilities Recorded at Fair Value on a Recurring Basis

The following tables present our assets and liabilities that are measured at fair value on a recurring basis by fair value hierarchy level at the dates presented:

Assets Recorded at Fair Value on a Nonrecurring Basis

We may be required to measure certain assets and liabilities at fair value on a nonrecurring basis. These assets and liabilities are recorded at the lower of cost or fair value in our consolidated financial statements and are remeasured only when events or circumstances indicate impairment. At September 30, 2026, individually evaluated loans of $7.8 million were measured at fair value on a nonrecurring basis and classified as Level 3. At December 31, 2025 individually evaluated loans of $10.6 million were classified as Level 3 and $5.3 million were classified as Level 2. There were no liabilities measured at fair value on a nonrecurring basis at both September 30, 2026 and December 31, 2025.

Significant unobservable inputs used in the fair value measurements of Level 3 assets on a nonrecurring basis at September 30, 2026 and December 31, 2025 were as follows:

Fair Value of Financial Instruments

The following tables present the carrying values and fair values of our financial instruments at the dates presented:

NOTE 4. SECURITIES

The following table presents the fair value of our securities portfolio at the dates presented:

The following table presents the amortized cost and fair value of available-for-sale debt securities at the dates presented:

(1)Excludes interest receivable of $3.2 million at September 30, 2026 and $3.3 million at December 31, 2025. Interest receivable is included in other assets in the Consolidated Balance Sheets.

(2)Collateralized mortgage obligations and residential mortgage-backed securities consist primarily of securities guaranteed by Fannie Mae, Freddie Mac and Ginnie Mae.

The following tables present the fair value and the age of gross unrealized losses on available-for-sale debt securities by investment category at the dates presented:

We evaluate securities with unrealized losses quarterly to determine if the decline in fair value has resulted from credit impairment or other factors. We do not believe any individual unrealized loss as of September 30, 2026 represents a credit impairment. The unrealized losses on debt securities were attributable to changes in interest rates and not related to the credit quality of the issuers. All debt securities were determined to be investment grade and paying principal and interest according to the contractual terms of the security. As of September 30, 2026, we do not intend to sell, and it is more likely than not that we will not be required to sell, the securities in an unrealized loss position before recovery of their amortized cost.

The following table presents net unrealized gains and losses, net of tax, on available-for-sale debt securities included in accumulated other comprehensive loss, for the periods presented:

The amortized cost and fair value of available-for-sale debt securities at September 30, 2026 by contractual maturity are included in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.

Debt securities are pledged in order to meet various regulatory and legal requirements. Restricted pledged securities had a carrying value of $41.9 million at September 30, 2026 and $38.3 million at December 31, 2025. Unrestricted pledged securities had a carrying value of $209.6 million at September 30, 2026 and $202.0 million at December 31, 2025. Any sales of or changes to the pledged status of restricted pledged securities requires approval of the beneficiary. Approval is not required in order to sell or make changes to the pledged status for unrestricted pledged securities.

NOTE 5. LOANS AND ALLOWANCE FOR CREDIT LOSSES

Loans and Loans Held for Sale

Loans are presented net of unearned income. Unearned income consisted of net deferred loan fees and costs of $3.1 million at September 30, 2026 and $4.8 million at December 31, 2025 and a discount related to purchase accounting fair value adjustments of $1.6 million at September 30, 2026 and $2.0 million at December 31, 2025.

The following table summarizes the composition of our loan portfolio at the dates presented:

(1)Excludes interest receivable of $33.4 million at September 30, 2026 and $33.4 million at December 31, 2025. Interest receivable is included inother assets in the Consolidated Balance Sheets.

Modifications to Borrowers Experiencing Financial Difficulty

The following tables present the amortized cost of loans to borrowers experiencing financial difficulty by portfolio segment and type of modification during the periods presented:

The following tables describe the effect of loan modifications made to borrowers experiencing financial difficulty during the periods presented:

We closely monitor the performance of the loans that are modified to borrowers experiencing financial difficulty to understand the effectiveness of the modification efforts. The following tables present an aging analysis since the date of modification for loans to borrowers experiencing financial difficulty that were modified in the last 12 months as of the dates presented:

A payment default is defined as a loan having a payment past due 90 days or more. There were three payment defaults on previously modified loans to borrowers experiencing financial difficulty in the amount of $11.3 million during the three months ended September 30, 2026 andfive payment defaults in the amount of $25.0 million during the nine months ended September 30, 2026 compared tothree payment defaults in the amount of $0.2 million during the three months ended September 30, 2025 andfive payment defaults in the amount of $3.7 million during the nine months ended September 30, 2025. Additionally, we hadeleven commitments to lend an additional $0.7 million to borrowers experiencing financial difficulty that had a modification during the twelve months ended September 30, 2026 andeleven commitments to lend an additional $0.2 million to borrowers experiencing financial difficulty that had a modification during the same period in 2025.

The effect of modifications made to borrowers experiencing financial difficulty is already included in the allowance for credit losses, or ACL, because of the measurement methodologies used to estimate the ACL, therefore, a change to the ACL is generally not recorded upon modification. If principal forgiveness is provided, that portion of the loan will be charged-off, resulting in a reduction of the amortized cost basis and a corresponding adjustment to the ACL. An assessment of whether the borrower is experiencing financial difficulty is made on the date of a modification.

Allowance for Credit Losses

We maintain an ACL, at a level determined to be adequate to absorb estimated expected credit losses within the loan portfolio over the contractual life of an instrument that considers our historical loss experience, current conditions and forecasts of future economic conditions as of the balance sheet date. We develop and document a systematic ACL methodology based on the following portfolio segments: 1) CRE, 2) C&I, 3) Commercial Construction, 4) Business Banking, 5) Consumer Real Estate and 6) Other Consumer.

The following are key risks within each portfolio segment:

CRE—Loans secured by commercial purpose real estate, including both owner-occupied properties and investment properties for various purposes such as hotels, retail, multifamily and health care. Operations of the individual projects and global cash flows of the debtors are the primary sources of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and the business prospects of the lessee, if the project is not owner-occupied.

C&I—Loans made to operating companies or manufacturers for the purpose of production, operating capacity, accounts receivable, inventory or equipment financing. Cash flow from the operations of the company is the primary source of repayment for these loans. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the industry of the company. Collateral for these types of loans often does not have sufficient value in a distressed or liquidation scenario to satisfy the outstanding debt.

Commercial Construction—Loans made to finance construction of buildings or other structures, as well as to finance the acquisition and development of raw land for various purposes. While these loans are generally confined to the construction period, if there are problems, the project may not be completed, and as such, may not provide sufficient cash flow on its own to service the debt or have sufficient value in a liquidation to cover the outstanding principal. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the type of project and the experience and resources of the developer.

Business Banking—Commercial purpose loans made to small businesses that are standard, non-complex products evaluated through a streamlined credit approval process that has been designed to maximize efficiency while maintaining high credit quality standards that meet small business market customers’ needs. The business banking portfolio is monitored by utilizing a standard and closely managed process focusing on behavioral and performance criteria. The condition of the local economy is an important indicator of risk, but there are also more specific risks depending on the collateral type and business.

Consumer Real Estate—Loans secured by first and second liens such as 1-4 family residential mortgages, home equity loans and home equity lines of credit. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The state of the local housing market can also have a significant impact on this segment because low demand and/or declining home values can limit the ability of borrowers to sell a property and satisfy the debt.

Other Consumer—Loans made to individuals that may be secured by assets other than 1-4 family residences, as well as unsecured loans. This segment includes auto loans, unsecured loans and lines of credit. The primary source of repayment for these loans is the income and assets of the borrower. The condition of the local economy, in particular the unemployment rate, is an important indicator of risk for this segment. The value of the collateral, if there is any, is less likely to be a source of repayment due to less certain collateral values.

Management monitors various credit quality indicators for the commercial, business banking and consumer loan portfolios, including changes in risk ratings, nonperforming status and delinquency on a monthly basis.

We monitor the commercial and business banking loan portfolio through an internal risk rating system. Loan risk ratings are assigned based upon the creditworthiness of the borrower and are reviewed on an ongoing basis according to our internal policies. Loans within the pass rating generally have a lower risk of loss than loans risk rated as special mention or substandard.

Our risk ratings are consistent with regulatory guidance and are as follows:

Pass—The loan is currently performing and is of high quality.

Special Mention—A special mention loan has potential weaknesses that warrant management’s close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects or in the strength of our credit position at some future date.

Substandard—A substandard loan is not adequately protected by the net worth and/or paying capacity of the borrower or by the collateral pledged, if any. Substandard loans have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. These loans are characterized by the distinct possibility that we will sustain some loss if the deficiencies are not corrected.

Doubtful—Loans classified doubtful have all the weaknesses inherent in those classified substandard with the added characteristic that the weaknesses make collection or liquidation in full, on the basis of currently known facts, conditions and values, highly questionable and improbable. The following tables present loan balances by year of origination and internally assigned risk rating for our portfolio segments at the dates presented:

The following tables present the aging analysis of past due loans segregated by class of loans at the dates presented:

The following tables present loans on nonaccrual status by class of loan for the year-to-date periods presented:

(1)Represents only cash payments received and applied to interest on nonaccrual loans.

(1)Represents only cash payments received and applied to interest on nonaccrual loans.

The following tables present loans that are individually evaluated and collateral-dependent at the dates presented:

The following tables present activity in the ACL for the periods presented:

The following tables present activity in the ACL for the periods presented:

NOTE 6. DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES

Derivatives Designated as Hedging Instruments

The following table indicates the amounts representing the value of derivative assets and derivative liabilities at the dates presented:

The following table indicates the gross amounts of interest rate swap derivative assets and derivative liabilities, the amounts offset and the carrying values in the Consolidated Balance Sheets at the dates presented:

Amounts reported in OCI related to derivatives that are designated as hedging instruments are reclassified to interest income as interest payments are received on variable rate assets. We estimate that an additional $1.1 million will be reclassified as a decrease to interest income in the next 12 months. Our current interest rate swap agreements had original terms ofthree tofive years with maturity dates extending into July 2027.

The following table indicates the gain (loss) recognized in income on derivatives not designated as hedging instruments for the periods presented:

NOTE 7. TAX CREDIT EQUITY INVESTMENTS

We invest in low income housing tax credit, or LIHTC, and historic tax credit, or HTC, partnerships as part of our responsibilities under the Community Reinvestment Act and due to their favorable federal income tax benefits. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. No impairment losses were recognized for the three and nine months ended September 30, 2026 and 2025.

The following table presents the balances included in the Consolidated Balance Sheets at the dates presented:

The following table summarizes the amortization expense and tax credits included in income tax expense in the Condensed Consolidated Statements of Comprehensive Income for the periods presented:

NOTE 8. COMMITMENTS AND CONTINGENCIES

Commitments

In the normal course of business, we offer off-balance sheet credit arrangements to enable our customers to meet their financing objectives. These instruments involve, to varying degrees, elements of credit and interest rate risk in excess of the amount recognized in the consolidated financial statements. Our exposure to credit loss, in the event the customer does not satisfy the terms of the agreement, equals the contractual amount of the obligation less the value of any collateral. We apply the same credit policies in making commitments and standby letters of credit that are used for the underwriting of loans to customers. Commitments generally have fixed expiration dates, annual renewals or other termination clauses and may require payment of a fee. Because many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements.

The following table sets forth our commitments and letters of credit at the dates presented:

Litigation

In the normal course of business, we are subject to various legal and administrative proceedings and claims. While any type of litigation contains a level of uncertainty, we believe that the outcome of such proceedings or claims pending will not have a material adverse effect on our consolidated financial position or results of operations.

NOTE 9. OTHER COMPREHENSIVE INCOME (LOSS)

The following table presents the change in components of other comprehensive income (loss) for the periods presented, net of tax effects:

NOTE 10. SHARE REPURCHASE PLAN

On January 21, 2026, the Board of Directors of S&T Bancorp, Inc. authorized a $100.0 million share repurchase program. The repurchase authorization permitted S&T to repurchase shares of S&T's common stock from time to time through a combination of open market and privately negotiated repurchases up to the authorized $100.0 million aggregate value of S&T's common stock.

On July 22, 2026, the Board of Directors of S&T Bancorp, Inc. authorized a new $100.0 million share repurchase program. The new program replaced the existing share repurchase program effective July 27, 2026, and is set to expire August 31, 2027. The remaining capacity of $2.8 million under the existing share repurchase program was terminated. The new program authorizes the share repurchase of S&T's common stock from time to time through a combination of open market and privately negotiated repurchases up to the authorized $100.0 million aggregate value of S&T's common stock. The specific timing, price and quantity of repurchases will be at the discretion of S&T and will depend on a variety of factors, including general market conditions, the trading price of the common stock, applicable securities laws and other legal and contractual requirements, as well as S&T's financial performance. The repurchase program does not obligate S&T to repurchase any particular number of shares and may be extended, modified or discontinued at any time.

There wereno repurchases during the three months ended September 30, 2026. During the nine months ended September 30, 2026,2,221,024 common shares were repurchased at an average price of $43.75 per share for a total share cost of $97.2 million, excluding excise tax and commissions. There were no repurchases during the three and nine months ended September 30, 2025. At September 30, 2026, there was $100.0 million in capacity remaining under the plan.