<general_context>
	- Current date: 2026-10-28 12:59 UTC.
</general_context>
<company_context>
	- Ticker: ACNB.
	- Company: ACNB.
</company_context>


                <data>
                    <label>ACNB 8-K, date: 2026-10-28 12:59 UTC</label>
                    <content>### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549
\_\_\_\_\_\_\_\_\_\_\_\_\_\_
#### FORM 8-K

### CURRENT REPORT

#### Pursuant to Section 13 or 15\(d\)

#### of the Securities Exchange Act of 1934
\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Date of Report \(Date of earliest event reported\): October 27, 2026
#### ACNB Corporation
\(Exact name of Registrant as specified in its charter\)
| Pennsylvania    |     | 1-35015     |     | 23-2233457         |
| \(State or other 
 jurisdiction of 
 incorporation\)  |     | -Commission 
 File Number |     | -IRS Employer      
 Identification No. |

| 16 Lincoln Square,Gettysburg,PA          |     |     17325 |
| \(Address of principal executive offices\) |     | -Zip Code |

|                                                      |     | 717.334.3161 |
| \(Registrant’s telephone number, including area code\) |     |              |

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the Registrant under any of the following provisions \( see General Instruction A.2. below\):

☐Written communications pursuant to Rule 425 under the Securities Act \(17 CFR 230.425\)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act \(17 CFR 240.14a-12\)

☐ Pre-commencement communications pursuant to Rule 14d-2\(b\) under the Exchange Act \(17 CFR 240.14d-2\(b\)\)

☐ Pre-commencement communications pursuant to Rule 13e-4\(c\) under the Exchange Act \(17 CFR 240.13e-4\(c\)\)

Indicate by check mark whether the Registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 \(§230.405 of this chapter\) or Rule 12b-2 of the Securities Exchange Act of 1934 \(§240.12b-2 of this chapter\).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13\(a\) of the Exchange Act. ☐

Securities registered pursuant to Section 12\(b\) of the Act:

| Title Of Each Class                     |     | Trading Symbol\(s\) |     | Name Of Each Exchange On Which Registered |
| Common Stock, $2.50 par value per share |     | ACNB              |     | The NASDAQ Stock Market, LLC              |

#### CURRENT REPORT ON FORM 8-K

#### ITEM 8.01

#### Other Events
As more fully described in the attached press release dated October 28, 2026, the Board of Directors \(“Board”\) of ACNB Corporation \(“ACNB”\) approved and declared the regular quarterly cash dividend for the fourth quarter of 2026 on October 27, 2026. The regular quarterly cash dividend of $0.46 per share of common stock is payable on December 15, 2026, to shareholders of record as of December 1, 2026.

In addition, on October 27, 2026, the Board of ACNB declared a special cash dividend of $0.75 per share of ACNB common stock payable on December 15, 2026, to shareholders of record as of December 1, 2026.

A copy of the press release announcing these actions is attached hereto as Exhibit 99.1 and is incorporated herein by reference. The information furnished under this Item 8.01 of this Current Report on Form 8-K shall not be deemed to be filed for purposes of the Securities Exchange Act of 1934.

#### ITEM 9.01

#### Financial Statements and Exhibits
\(d\) Exhibits.

Exhibit Number Description

99.1 ACNB Corporation Press Release dated October 28, 2026 .

104 Cover Page Interactive Data File \(embedded within the Inline XBRL document\).

### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this Current Report on Form 8-K to be signed on its behalf by the undersigned, thereunto duly authorized.

| Dated: |     | October 28, 2026 |     | ACNB CORPORATION\(Registrant\)                          
 /s/ Kevin J. Hayes                                    |
|:-------|:----|:-----------------|:----|:------------------------------------------------------|
|        |     |                  |     | Kevin J. Hayes                                        |
|        |     |                  |     | Senior Vice President/                                |
|        |     |                  |     | General Counsel, Secretary & Chief Governance Officer |</content>
                </data>
            

                <data>
                    <label>Press release on regular and special cash dividends</label>
                    <content>[IMAGE:  | Source: pressrelease2026-fourthq001.jpg] [COLOR: white]      PRESS RELEASE    FOR IMMEDIATE RELEASE          Contact: Kevin J. Hayes       SVP/General Counsel,        Secretary & Chief        Governance Officer       717.339.5161       khayes@acnb.com    ACNB CORPORATION ANNOUNCES  FOURTH QUARTER OF 2026 REGULAR AND SPECIAL CASH DIVIDENDS    GETTYSBURG, PA, October 28, 2026 --- ACNB Corporation \(NASDAQ: ACNB\), financial  holding company for ACNB Bank and ACNB Insurance Services, Inc., announced today that the Board of  Directors has declared both a regular quarterly cash dividend of $0.46 per share and a special cash dividend  of $0.75 per share on the Corporation's common stock.  The regular quarterly cash dividend of $0.46 per share represents an increase of 9.5% from the  quarterly cash dividend of $0.42 per share paid in the prior quarter. Combined with the special cash dividend  of $0.75 per share, shareholders will receive total cash dividends of $1.21 per share. Both the regular  quarterly cash dividend and the special cash dividend will be payable on December 15, 2026, to  shareholders of record as of December 1, 2026.  "Our Board's decision to approve both a quarterly dividend increase and a special dividend reflects  the exceptional financial strength our Company has demonstrated over the past several years," said James  P. Helt, President and Chief Executive Officer of ACNB Corporation. "This marks the second increase to  [/COLOR]

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[IMAGE:  | Source: pressrelease2026-fourthq002.jpg] [COLOR: white]  ACNB Corporation  Press Release/Fourth Quarter 2026 Regular and Special Dividends  October 28, 2026  Page 2 of 4       our regular dividend and our second special dividend in 2026, underscoring our commitment to delivering  meaningful returns to shareholders while maintaining the capital, liquidity, and balance sheet strength  necessary to support future growth and continue serving our communities."  ACNB Corporation has a long-standing history of providing returns to shareholders through regular  cash dividends while maintaining a conservative approach to capital management and supporting future  growth opportunities. Including these declared dividends, ACNB Corporation will have paid total cash  dividends of $2.93 per share during 2026, consisting of $1.68 in regular cash dividends and $1.25 in special  cash dividends.  The total amount of dividends that will be paid per share in 2026 represents an increase of  approximately 112% over the $1.38 per share paid in 2025.   ACNB Corporation, headquartered in Gettysburg, PA, is the independent $3.30 billion financial  holding company for the wholly-owned subsidiaries of ACNB Bank, Gettysburg, PA, including its operating  divisions Traditions Bank and Traditions Mortgage, and ACNB Insurance Services, Inc., Westminster, MD.  Originally founded in 1857, ACNB Bank serves its marketplace with banking and wealth management  services, including trust and retail brokerage, via a network of 33 community banking offices and two  Limited Purpose Offices located in the Pennsylvania counties of Adams, Cumberland, Franklin, Lancaster,  York, and Berks and the Maryland counties of Baltimore, Carroll and Frederick. ACNB Insurance Services,  Inc. is a full-service insurance agency with licenses in 46 states. The agency offers a broad range of property,  casualty, health, life and disability insurance serving personal and commercial clients through office  locations in Westminster, MD, and Gettysburg, PA. For more information regarding ACNB Corporation  and its subsidiaries, please visit investor.acnb.com.  [/COLOR]

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[IMAGE:  | Source: pressrelease2026-fourthq003.jpg] [COLOR: white]  ACNB Corporation  Press Release/Fourth Quarter 2026 Regular and Special Dividends  October 28, 2026  Page 3 of 4       #           #           #  FORWARD-LOOKING STATEMENTS - In addition to historical information, this press release may contain forward-looking  statements. Examples of forward-looking statements include, but are not limited to, \(a\) projections or statements regarding future  earnings, expenses, net interest income, other income, earnings or loss per share, asset mix and quality, growth prospects, capital  structure, and other financial terms, \(b\) statements of plans and objectives of Management or the Board of Directors, and \(c\)  statements of assumptions, such as economic conditions in the Corporation’s market areas. Such forward-looking statements can be  identified by the use of forward-looking terminology such as “believes”, “expects”, “may”, “intends”, “will”, “should”, “anticipates”,  or the negative of any of the foregoing or other variations thereon or comparable terminology, or by discussion of strategy. Forward- looking statements are subject to certain risks and uncertainties such as national, regional and local economic conditions, competitive  factors, and regulatory limitations. Actual results may differ materially from those projected in the forward-looking statements. Such  risks, uncertainties, and other factors that could cause actual results and experience to differ from those projected include, but are not  limited to, the following: short-term and long-term effects of inflation and rising costs on the Corporation, customers and economy;  banking instability caused by bank failures and financial uncertainty of various banks which may adversely impact the Corporation and  its securities and loan values, deposit stability, capital adequacy, financial condition, operations, liquidity, and results of operations;  effects of governmental and fiscal policies, as well as legislative and regulatory changes; effects of new laws and regulations \(including  laws and regulations concerning taxes, banking, securities and insurance\) and their application with which the Corporation and its  subsidiaries must comply; impacts of the capital and liquidity requirements of the Basel III standards; effects of changes in accounting  policies and practices, as may be adopted by the regulatory agencies, as well as the Financial Accounting Standards Board and other  accounting standard setters; ineffectiveness of the business strategy due to changes in current or future market conditions; future actions  or inactions of the United States government, including the effects of short-term and long-term federal budget and tax negotiations and  a failure to increase the government debt limit or a prolonged shutdown of the federal government; effects of economic conditions  particularly with regard to the negative impact of any pandemic, epidemic or health-related crisis and the responses thereto on the  operations of the Corporation and current customers, specifically the effect of the economy on loan customers’ ability to repay loans;  effects of competition, and of changes in laws and regulations on competition, including industry consolidation and development of  competing financial products and services; inflation, securities market and monetary fluctuations; risks of changes in interest rates on  the level and composition of deposits, loan demand, and the values of loan collateral, securities, and interest rate protection  agreements, as well as interest rate risks; difficulties in acquisitions and integrating and operating acquired business operations,  including information technology difficulties; challenges in establishing and maintaining operations in new markets; effects of  technology changes; effects of general economic conditions and more specifically in the Corporation’s market areas; failure of  assumptions underlying the establishment of reserves for credit losses and estimations of values of collateral and various financial assets  and liabilities; acts of war or terrorism or geopolitical instability; disruption of credit and equity markets; ability to manage current  levels of impaired assets; loss of certain key officers; ability to maintain the value and image of the Corporation’s brand and protect the  Corporation’s intellectual property rights; continued relationships with major customers; and, potential impacts to the Corporation from  continually evolving cybersecurity and other technological risks and attacks, including additional costs, reputational damage, regulatory  penalties, and financial losses. We caution readers not to place undue reliance on these forward-looking statements. They only reflect  Management’s analysis as of this date. The Corporation does not revise or update these forward-looking statements to reflect events or  changed circumstances. Please carefully review the risk factors described in other documents the Corporation files from time to time  with the SEC, including the Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q. Please also carefully review any  Current Reports on Form 8-K filed by the Corporation with the SEC.    ACNB #2026-15  October 28, 2026  [/COLOR]

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                </data>
            