<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-10-09</periodOfReport>

    <issuer>
        <issuerCik>0000903419</issuerCik>
        <issuerName>ALERUS FINANCIAL CORP</issuerName>
        <issuerTradingSymbol>ALRS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001925331</rptOwnerCik>
            <rptOwnerName>Bolton Jeffrey</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>401 DEMERS AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>GRAND FORKS</rptOwnerCity>
            <rptOwnerState>ND</rptOwnerState>
            <rptOwnerZipCode>58201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7729</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7729</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1309</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9038</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Received in exchange for 6,183.611 shares of HMN Financial, Inc. (&quot;HMNF&quot;) common stock in connection with merger (the &quot;Merger&quot;) of HMN Financial, Inc. with and into Alerus Financial Corporation (&quot;Alerus&quot;), effective October 9, 2024 (the &quot;Effective Time&quot;). Pursuant to the terms of the Agreement and Plan of Merger, dated May 14, 2024, between Alerus and HMNF, as of the Effective Time, each issued and outstanding share of HMNF common stock converted into the right to receive 1.25 shares of Alerus common stock, with payment of cash in lieu of fractional shares of Alerus common stock.</footnote>
        <footnote id="F2">On the Effective Date, the closing price of HMNF's common stock was $27.99 per share, and the closing price of Alerus' common stock was $22.28 per share.</footnote>
        <footnote id="F3">All shares were acquired pursuant to an annual director award issued under the Alerus Financial Corporation 2019 Equity Incentive Plan.</footnote>
        <footnote id="F4">Includes 1,309 shares of restricted stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Nicholas Brenckman, by power of attorney</signatureName>
        <signatureDate>2024-10-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
