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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-10-16</periodOfReport>

    <issuer>
        <issuerCik>0000101382</issuerCik>
        <issuerName>UMB FINANCIAL CORP</issuerName>
        <issuerTradingSymbol>UMBF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001229026</rptOwnerCik>
            <rptOwnerName>RILINGER DENNIS R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1010 GRAND BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KANSAS CITY</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64106</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP and General Counsel</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-10-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1274</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.17</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6593.9479</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1745.9357</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9484</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.17</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-10-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1274</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.17</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                    <footnoteId id="F3"/>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2006-10-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1274</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On May 30, 2006, the common stock of UMB Financial Corporation split 2-for-1 resulting in additional shares</footnote>
        <footnote id="F4">Options vest 40% 2 years after the date of grant; 60% 3 years after the date of grant; 80% 4 years after the date of grant; and 100% 4 years 11 months after the date of grant.</footnote>
        <footnote id="F3">The number of shares and price have been adjusted from what was originally reported to reflect a 2-for-1 split of UMB Financial Corporation Stock on May 30, 2006.</footnote>
        <footnote id="F2">Reflects ESOP allocations and dispositions that have occurred since the date of the reporting person's last ownership report.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John C. Pauls, Attorney in Fact</signatureName>
        <signatureDate>2006-10-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-10-16
0000101382
UMB FINANCIAL CORP
UMBF
0001229026
RILINGER DENNIS R
1010 GRAND BLVD.
KANSAS CITY
MO
64106
0
1
0
0
EVP and General Counsel
Common Stock
2006-10-16
4
M
0
1274
15.17
A
6593.9479
D
Common Stock
1745.9357
I
By ESOP
Common Stock
9484
I
By IRA
Stock Options (Right to buy)
15.17
2006-10-16
4
M
0
1274
15.17
D
2006-10-18
Common Stock
1274
0
D
On May 30, 2006, the common stock of UMB Financial Corporation split 2-for-1 resulting in additional shares
Options vest 40% 2 years after the date of grant; 60% 3 years after the date of grant; 80% 4 years after the date of grant; and 100% 4 years 11 months after the date of grant.
The number of shares and price have been adjusted from what was originally reported to reflect a 2-for-1 split of UMB Financial Corporation Stock on May 30, 2006.
Reflects ESOP allocations and dispositions that have occurred since the date of the reporting person's last ownership report.
John C. Pauls, Attorney in Fact
2006-10-16