<SEC-DOCUMENT>0000715579-25-000008.txt : 20250106
<SEC-HEADER>0000715579-25-000008.hdr.sgml : 20250106
<ACCEPTANCE-DATETIME>20250106125123
ACCESSION NUMBER:		0000715579-25-000008
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250101
FILED AS OF DATE:		20250106
DATE AS OF CHANGE:		20250106

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Weber Jason H
		CENTRAL INDEX KEY:			0001910158
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-35015
		FILM NUMBER:		25510037

	MAIL ADDRESS:	
		STREET 1:		1830 BOULDER DRIVE
		CITY:			DOWNINGTOWN
		STATE:			PA
		ZIP:			19335

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ACNB CORP
		CENTRAL INDEX KEY:			0000715579
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		ORGANIZATION NAME:           	02 Finance
		IRS NUMBER:				232233457
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		16 LINCOLN SQUARE
		STREET 2:		P O BOX 3129
		CITY:			GETTYSBURG
		STATE:			PA
		ZIP:			17325
		BUSINESS PHONE:		7173343161

	MAIL ADDRESS:	
		STREET 1:		P O BOX 3129
		STREET 2:		16 LINCOLN SQUARE
		CITY:			GETTYSBURG
		STATE:			PA
		ZIP:			17325
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>wk-form4a_1736185877.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2025-01-01</periodOfReport>

    <dateOfOriginalSubmission>2025-01-03</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000715579</issuerCik>
        <issuerName>ACNB CORP</issuerName>
        <issuerTradingSymbol>ACNB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001910158</rptOwnerCik>
            <rptOwnerName>Weber Jason H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>16 LINCOLN SQUARE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GETTYSBURG</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>17325</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP, Treasurer &amp; CFO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>ACNB Corporation Common</value>
            </securityTitle>
            <transactionDate>
                <value>2025-01-01</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2025-01-02</value>
                <footnoteId id="F1"/>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>869.4192</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>39.655</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5648.3395</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The date of execution was determined in accordance with SEC Rule 16a-3(g)(2) and (g)(4).</footnote>
        <footnote id="F2">The shares disposed were withheld by the Issuer and/or its subsidiary ACNB Bank for payment of the tax liability, on restricted shares previously awarded on March 15, 2023 and March 15, 2024 under the ACNB Bank Variable Compensation Plan and pursuant to the ACNB Corporation 2018 Omnibus Stock Incentive Plan, that vested on January 1, 2025, in accordance with SEC Rule 16b-3. For clarification, the executive did not sell the shares.</footnote>
        <footnote id="F3">Due to an administrative error, the previously reported number of shares in this Code F Transaction on January 3, 2025, was incorrectly stated to be 1,246.1942. This amended Form 4 reflects the accurate number of shares involved in the transaction.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jason H. Weber</signatureName>
        <signatureDate>2025-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
