<SEC-DOCUMENT>0001193125-17-087429.txt : 20170317
<SEC-HEADER>0001193125-17-087429.hdr.sgml : 20170317
<ACCEPTANCE-DATETIME>20170317163832
ACCESSION NUMBER:		0001193125-17-087429
CONFORMED SUBMISSION TYPE:	8-K
PUBLIC DOCUMENT COUNT:		3
CONFORMED PERIOD OF REPORT:	20170317
ITEM INFORMATION:		Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant
ITEM INFORMATION:		Financial Statements and Exhibits
FILED AS OF DATE:		20170317
DATE AS OF CHANGE:		20170317

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CULLEN/FROST BANKERS, INC.
		CENTRAL INDEX KEY:			0000039263
		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
		IRS NUMBER:				741751768
		STATE OF INCORPORATION:			TX
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		8-K
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13221
		FILM NUMBER:		17698542

	BUSINESS ADDRESS:	
		STREET 1:		100 W HOUSTON ST
		CITY:			SAN ANTONIO
		STATE:			TX
		ZIP:			78205
		BUSINESS PHONE:		210-220-4011

	MAIL ADDRESS:	
		STREET 1:		POST OFFICE BOX 1600
		CITY:			SAN ANTONIO
		STATE:			TX
		ZIP:			78296-1600

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	CULLEN FROST BANKERS INC
		DATE OF NAME CHANGE:	19920703

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FROST BANK CORP
		DATE OF NAME CHANGE:	19770823
</SEC-HEADER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>d345021d8k.htm
<DESCRIPTION>FORM 8-K
<TEXT>
<HTML><HEAD>
<TITLE>Form 8-K</TITLE>
</HEAD>
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 <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:4pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>UNITED STATES </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>SECURITIES AND EXCHANGE COMMISSION </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>Washington, D.C. 20549 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>FORM 8-K
</B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>CURRENT REPORT </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>PURSUANT
TO SECTION 13 OR 15(d) </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>OF THE SECURITIES EXCHANGE ACT OF 1934 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): March&nbsp;17, 2017 </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:24pt; font-family:Times New Roman" ALIGN="center"><B>CULLEN/FROST BANKERS, INC. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Exact name of registrant as specified in its charter) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


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<TD VALIGN="top" ALIGN="center"><B>Texas</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>001-13221</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>74-1751768</B></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(State or other jurisdiction of</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>incorporation or organization)</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Commission</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>File Number)</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(I.R.S. Employer</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Identification Number)</B></P></TD></TR>
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<TD VALIGN="top" COLSPAN="3" ALIGN="center"><B>100 West Houston Street, San Antonio, Texas</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>78205</B></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" COLSPAN="3" ALIGN="center"><B>(Address of Principal Executive Offices)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(Zip Code)</B></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(210) 220-4011 </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Registrant&#146;s telephone number) </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Not Applicable </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Former
name or former address, if changed since last report) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Check the appropriate box below
if the Form 8-K is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions: </P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">&#9744;</TD>
<TD ALIGN="left" VALIGN="top">Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">&#9744;</TD>
<TD ALIGN="left" VALIGN="top">Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left">&#9744;</TD>
<TD ALIGN="left" VALIGN="top"><B></B>Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B></B>&#9744;<B></B><B></B></TD>
<TD ALIGN="left" VALIGN="top"><B></B>Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4 (c)) </TD></TR></TABLE> <P STYLE="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Item&nbsp;2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet
Arrangement of a Registrant </B></P> <P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">On March&nbsp;17, 2017, Cullen/Frost Bankers, Inc. (the &#147;Company&#148;) completed the issuance and sale of
$100,000,000 aggregate principal amount of the Company&#146;s 4.500% Subordinated Notes due March&nbsp;17, 2027 (the &#147;Subordinated Notes&#148;). The Notes were offered pursuant to the prospectus supplement dated March&nbsp;10, 2017,
constituting part of the Registration Statement on Form S-3 (No. 333-214987) (the &#147;Registration Statement&#148;) that became effective when filed with the Securities and Exchange Commission on December&nbsp;8, 2016. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Subordinated Notes were issued under the Subordinated Notes Indenture, dated as of February&nbsp;15, 2007, between the Company and The Bank of New York,
as trustee (the &#147;Base Indenture&#148;), as supplemented by the First Supplemental Indenture, dated as of March&nbsp;17, 2017, between the Company and The Bank of New York Mellon, as trustee (the &#147;First Supplemental Indenture&#148;, and
together with the Base Indenture, the &#147;Indenture&#148;). The Subordinated Notes will bear interest at the rate of 4.500%&nbsp;per annum, with interest payable semiannually in arrears on March&nbsp;17 and September&nbsp;17 of each year,
commencing September&nbsp;17, 2017. The Subordinated Notes will mature on March&nbsp;17, 2027. On or after February&nbsp;17, 2027, the Company will have the option to redeem the Subordinated Notes, in whole or in part, at a redemption price equal to
100% of the principal amount of the Subordinated Notes to be redeemed plus accrued and unpaid interest. The Company&#146;s ability to exercise such redemption option is subject to the prior approval of the Board of Governors of the Federal Reserve
System. Holders should not expect the Subordinated Notes to be redeemed prior to their scheduled maturity. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">The Company&#146;s obligation to make payments
of principal and interest on the Subordinated Notes is subordinate and junior in right of payment to all of its &#147;Senior Debt&#148; (as defined in the Indenture). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">This Current Report on Form 8-K is being filed for the purpose of filing Exhibits 4.1, 4.2, 5.1 and 23.1 as exhibits to the Registration Statement and such
exhibits are hereby incorporated by reference into the Registration Statement. The foregoing description of the Notes is qualified in its entirety by reference to the First Supplemental Indenture and Form of Subordinated Notes filed as Exhibits 4.1
and 4.2 hereto, respectively, and the Base Indenture which was filed as Exhibit 4.6 to the Company&#146;s Registration Statement on Form S-3 filed on December 8, 2016. </P>
<P STYLE="margin-top:18pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Item&nbsp;9.01 Financial Statements and Exhibits </B></P> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TR style = "page-break-inside:avoid">
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B>(d)</B></TD>
<TD ALIGN="left" VALIGN="top"><B>Exhibits</B> </TD></TR></TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="90%"></TD></TR>
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<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.10pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit&nbsp;No.</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.50pt; font-size:8pt; font-family:Times New Roman"><B>Description</B></P></TD></TR>


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<TD VALIGN="top" NOWRAP>4.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">First Supplemental Indenture, dated March 17, 2017, between Cullen/Frost Bankers, Inc. and The Bank of New York Mellon, as trustee.</TD></TR></TABLE>

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<TD WIDTH="90%"></TD></TR>

<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.10pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit&nbsp;No.</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.50pt; font-size:8pt; font-family:Times New Roman"><B>Description</B></P></TD></TR>


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<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;4.2</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Form of 4.500% Subordinated Notes due 2027 (included in Exhibit 4.1).</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
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<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;5.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Opinion of Stanley E. McCormick, Corporate Counsel to Cullen/Frost Bankers, Inc.</TD></TR>
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<TD VALIGN="top" NOWRAP>23.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Consent of Stanley E. McCormick, Corporate Counsel to Cullen/Frost Bankers, Inc. (included in Exhibit 5.1).</TD></TR>
</TABLE>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>SIGNATURE </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by
the undersigned, hereunto duly authorized. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"><B>CULLEN/FROST BANKERS, INC.</B></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
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<TD VALIGN="top">Date:&nbsp;&nbsp;&nbsp;&nbsp;March&nbsp;17, 2017</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Michael Benson</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name: Michael Benson</TD></TR>
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<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title: Senior Executive Vice President and Treasurer</TD></TR>
</TABLE>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>EXHIBIT INDEX </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


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<TD VALIGN="bottom" WIDTH="7%"></TD>
<TD WIDTH="90%"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.10pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit&nbsp;No.</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP> <P STYLE=" margin-top:0pt ; margin-bottom:0pt; border-bottom:1.00pt solid #000000; width:39.50pt; font-size:8pt; font-family:Times New Roman"><B>Description</B></P></TD></TR>


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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;4.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">First Supplemental Indenture, dated March 17, 2017, between Cullen/Frost Bankers, Inc. and The Bank of New York Mellon, as successor trustee.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;4.2</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Form of 4.500% Subordinated Notes due 2027 (included in Exhibit 4.1).</TD></TR>
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<TD VALIGN="top" NOWRAP>&nbsp;&nbsp;5.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Opinion of Stanley E. McCormick, Corporate Counsel to Cullen/Frost Bankers, Inc.</TD></TR>
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<TD VALIGN="top" NOWRAP>23.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Consent of Stanley E. McCormick, Corporate Counsel to Cullen/Frost Bankers, Inc. (included in Exhibit 5.1)</TD></TR>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 4.1 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000">&nbsp;</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CULLEN/FROST BANKERS, INC.
</B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><I>Company, </I></B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>AND </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><I></I></B><B>THE
BANK OF NEW YORK MELLON,</B><B><I> </I></B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B><I></I></B><B></B><B><I>Trustee </I></B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FIRST </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>SUPPLEMENTAL
</B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>INDENTURE </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Dated
as of </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">March 17, 2017 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">TO </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>SUBORDINATED </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>DEBT
SECURITIES </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>INDENTURE </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">Dated as of </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">February&nbsp;15,
2007 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>4.500% SUBORDINATED NOTES DUE MARCH 17, 2027 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000">&nbsp;</P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>TABLE OF CONTENTS </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
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<TD WIDTH="83%"></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD></TD>
<TD></TD>
<TD></TD></TR>
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<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" COLSPAN="2" ALIGN="center"><B>Page</B></TD>
<TD VALIGN="bottom">&nbsp;</TD></TR>


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<TD VALIGN="top">ARTICLE&nbsp;I</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">DEFINITIONS</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 101&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Definitions.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="2"></TD>
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<TD VALIGN="top">ARTICLE&nbsp;II</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">GENERAL TERMS AND CONDITIONS OF THE NOTES</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 201&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Designation and Principal Amount.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 202&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Form and Denomination of Notes.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 203&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Initial Limit on Amount of Series.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">2</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 204&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Further Issues Without Holders&#146; Consent.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 205&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Form and Payment.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 206&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Redemption; No Sinking Fund.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 207&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Acceleration of Maturity</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 208&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Defeasance and Covenant Defeasance</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">3</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 209&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Global Securities</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top">ARTICLE&nbsp;III</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">ORIGINAL ISSUE OF NOTES</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 301&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Original Issue of Notes.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top">ARTICLE&nbsp;IV</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">MISCELLANEOUS</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section&nbsp;401&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ratification of Indenture.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 402&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Conflict with Trust Indenture Act.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD HEIGHT="8" COLSPAN="3"></TD>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 403&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Effect of Headings and Table of Contents.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">4</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 404&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Successors and Assigns.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 405&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Separability Clause.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 406&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Benefits of Indenture.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 407&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Governing Law.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
<TD NOWRAP VALIGN="bottom">&nbsp;</TD></TR>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 408&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Waiver of Jury Trial.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 409&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Counterparts.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">5</TD>
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<TD VALIGN="top" COLSPAN="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Section 410&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Trustee.</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right">6</TD>
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 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-i- </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>THIS FIRST SUPPLEMENTAL INDENTURE</B>, dated as of March&nbsp;17, 2017 (this
&#147;Supplemental Indenture&#148;), between Cullen/Frost Bankers, Inc., a Texas corporation having its principal office at 100 West Houston Street, San Antonio, Texas 78205 (hereinafter called the &#147;Company,&#148; which term shall include any
successors and assigns pursuant to the terms of this Supplemental Indenture), and The Bank of New York Mellon (formerly known as The Bank of New York), a New York banking corporation, as Trustee hereunder (hereinafter called the
&#147;Trustee&#148;). <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>, the Company executed and delivered the Subordinated Debt Securities Indenture (the
&#147;Indenture&#148;), dated as of February&nbsp;15, 2007, to the Trustee, to provide for the issuance from time to time of the Company&#146;s subordinated debt securities (herein called the &#147;Securities&#148;), to be issued in one or more
series; <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>, pursuant to the terms of the Indenture, the Company desires to provide for the establishment of a series
of its Securities under the Indenture to be known as its &#147;4.500% Subordinated Notes due March&nbsp;17, 2027&#148; (the &#147;Notes&#148;), the form and substance of and the terms, provisions and conditions thereof to be set forth as provided in
the Indenture and this Supplemental Indenture; <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>, the Board of Directors of the Company, pursuant to resolutions
duly adopted on October&nbsp;27, 2016, has duly authorized the issuance of the Notes and the amendments to the Indenture provided for in this Supplemental Indenture, and has authorized the proper officers of the Company to execute any and all
appropriate documents necessary or appropriate to effect each such issuance; <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>, this Supplemental Indenture is being
entered into pursuant to the provisions of Section&nbsp;301, Section&nbsp;303 and Article IX of the Indenture; <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>,
the Company has requested that the Trustee execute and deliver this Supplemental Indenture; and <B> </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>WHEREAS</B>, all things
necessary to make this Supplemental Indenture a valid agreement of the Company, in accordance with its terms, and to make each of the Notes, when executed by the Company and authenticated and delivered by the Trustee or an authentication agent, the
valid obligations of the Company, have been performed, and the execution and delivery of this Supplemental Indenture has been duly authorized in all respects; <B> </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><B>NOW THEREFORE</B>, in consideration of the premises and the purchase and acceptance of the Notes by the Holders thereof, and for the
purpose of setting forth, as provided in the Indenture, the forms and terms of the Notes, the Company covenants and agrees with the Trustee, for the equal and proportionate benefit of all Holders of the Notes, as follows:<B> </B></P>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ARTICLE I </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>DEFINITIONS </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;101 <U>Definitions</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">For all purposes of this Supplemental Indenture, except as otherwise expressly provided or unless the context otherwise requires: </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(1) all references in this instrument to designated &#147;Articles,&#148; &#147;Sections&#148; and other subdivisions are to be designated
Articles, Sections and other subdivisions of this instrument unless the context otherwise requires; the words &#147;herein,&#148; &#147;hereof&#148; and &#147;hereunder&#148; and other words of similar import refer to this Supplemental Indenture as
a whole and not to any particular Article, Section or other subdivision; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(2) each capitalized term used herein that is defined in the
Indenture has the same meaning when used in this Supplemental Indenture, except to the extent specifically defined herein, in which case the meaning ascribed to it in this Supplemental Indenture shall control; and </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>(3) as used in this Supplemental Indenture, &#147;<I>Major Constituent Bank</I>&#148; means any Subsidiary which is organized as a
depository institution under Federal or state law and which represents 50% or more of the consolidated assets of the Company determined as of the date of the most recent audited financial statements of the Company.<I> </I></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">(4) for this series of Notes, &#147;<I>Regular Record Date</I>&#148; means the immediately preceding February 28 for an Interest Payment Date
falling on March 17 or the immediately preceding August 31 for an Interest Payment Date falling on September 17. </P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ARTICLE II </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>GENERAL TERMS AND CONDITIONS OF THE NOTES </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;201 <U>Designation and Principal Amount</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">There is hereby authorized and established a series of Securities under the Indenture, designated as the &#147;4.500% Subordinated Notes due
March&nbsp;17, 2027.&#148; </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;202 <U>Form and Denomination of Notes</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The definitive form of the Notes and the Trustee&#146;s Certificate of Authentication to be endorsed thereon shall be substantially in the
form set forth in Exhibit&nbsp;A attached hereto, which is incorporated herein and made part hereof. The Notes shall bear interest and have such other terms as are stated in the form of definitive Notes or in the Indenture, as supplemented by this
Supplemental Indenture. The Stated Maturity of the principal amount of the Notes shall be March&nbsp;17, 2027. The Notes shall be issued in denominations of $1,000 and any integral multiple thereof. The Notes shall not be issued as Original Issue
Discount Securities. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;203 <U>Initial Limit on Amount of Series</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Notes shall initially be limited to U.S. $100,000,000 in aggregate principal amount, and may, upon the execution and delivery of this
Supplemental Indenture or from time to time thereafter, be executed by the Company and delivered to the Trustee for authentication, and the </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">2 </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">
Trustee shall thereupon authenticate and deliver said Notes to or upon the delivery of a Company Order. Following the initial issuance of the Notes, the aggregate principal amount of Notes may be
increased as provided in Section&nbsp;204 hereof. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;204 <U>Further Issues Without Holders&#146; Consent</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Company may, without notice to or the consent of the Holders of the Notes, but in compliance with the terms of the Indenture and this
Supplemental Indenture, issue additional Notes having the same ranking, interest rate, maturity date and other terms as the Notes (other than the date of issuance, the issue price, the initial interest accrual date and the first Interest Payment
Date). Any such additional Notes will rank equally and ratably with the Notes. Any such additional Notes, together with the Notes initially issued hereunder, will constitute a single series of Securities for all purposes under the Indenture.
Notwithstanding anything to the contrary in the foregoing, no additional Notes may be issued unless they will be fungible with the Notes offered hereby for United States federal income tax and securities law purposes, and unless the additional Notes
have the same CUSIP number as these Notes. No additional Notes may be issued if any Default or Event of Default has occurred and is continuing with respect to the Notes. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;205 <U>Form and Payment</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Principal of, premium, if any, and interest on the Notes shall be payable in U.S. Dollars. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;206 <U>Redemption; No Sinking Fund</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Notes will be redeemable at the Company&#146;s option, subject to receipt of prior approval from the Board of Governors of the Federal
Reserve System, in whole or in part, at any time or from time to time, on or after February&nbsp;17, 2027, at a Redemption Price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest to, but not
including, the Redemption Date. No sinking fund will be provided with respect to the Notes. In no event shall any Holder of the Notes have the right to require the Company to call, redeem or repurchase the Notes, in whole or in part. Nothing in this
Section&nbsp;206 shall limit the ability of Holders of Notes to enforce their rights to the payment of principal, premium, if any, and interest on the Notes at maturity as provided in the Notes and in the Indenture, including Section&nbsp;507 of the
Indenture. If less than all of the Notes are to be redeemed, the Trustee will select the Notes to be redeemed in principal amounts of $1,000 or any integral multiple thereof on a pro rata basis, by lot or by such other method as the Trustee deems
fair and appropriate. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;207 <U>Acceleration of Maturity</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">For purposes of this series of Securities only, the phrase &#147;such a declaration of&#148; in the first sentence of the second paragraph of
Section&nbsp;502 of the Indenture is hereby deleted. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;208 <U>Defeasance and Covenant Defeasance</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Article XIII of the Indenture shall not be applicable to the Notes. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">3 </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;209 <U>Global Securities</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Notes shall be issued in the form of one or more permanent Global Securities, without coupons, registered in the name of the Depositary or
its nominee. Except as otherwise provided in Section&nbsp;305 of the Indenture, the Global Securities described above may be transferred by the Depositary, in whole but not in part, only to a nominee of the Depositary, or by a nominee of the
Depositary to the Depositary, or to a successor Depositary or to a nominee of such successor Depositary. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Owners of beneficial interests
in such Global Securities will not be considered the Holders thereof for any purpose under the Indenture. The rights of owners of beneficial interests in such Global Securities shall be exercised only through the Depositary. </P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ARTICLE III </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>ORIGINAL ISSUE OF
NOTES </B></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;301 <U>Original Issue of Notes</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Notes may, upon execution of this Supplemental Indenture, be executed by the Company and delivered to the Trustee for authentication, and
the Trustee shall, upon Company Order, authenticate and deliver such Notes as in such Company Order provided. </P> <P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">ARTICLE IV </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>MISCELLANEOUS </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;401 <U>Ratification of Indenture</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>The Indenture, as supplemented by this Supplemental Indenture, is in all respects ratified and confirmed, and this Supplemental
Indenture shall be deemed part of the Indenture in the manner and to the extent herein and therein provided; <I>provided, however</I>, that the provisions of this Supplemental Indenture shall apply solely with respect to the Notes and shall govern
in the event of any difference with the Indenture. <I> </I></P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;402 <U>Conflict with Trust Indenture Act</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">If any provision hereof limits, qualifies or conflicts with a provision of the Trust Indenture Act that is required under such Act to be a
part of and govern this Indenture, the provision of the Trust Indenture Act shall control. If any provision of this Supplemental Indenture modifies or excludes any provision of the Trust Indenture Act that may be so modified or excluded, the
provision of the Trust Indenture Act shall be deemed to apply to this Indenture as so modified or to be excluded, as the case may be. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;403 <U>Effect of Headings and Table of Contents</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Article and Section headings herein and the Table of Contents are for convenience only and shall not affect the construction hereof. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">4 </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;404 <U>Successors and Assigns</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">All covenants and agreements in this Supplemental Indenture by the Company shall bind its successors and assigns, whether expressed or not.
</P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;405 <U>Separability Clause</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In case any provision in this Supplemental Indenture or in the Notes shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or impaired thereby. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;406 <U>Benefits of
Indenture</U>. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Nothing in this Supplemental Indenture or in the Notes, express or implied, shall give to any Person, other than the
Holders of the Securities, the parties hereto and their successors hereunder, any benefit of any legal or equitable right, remedy or claim under this Supplemental Indenture. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;407 <U>Governing Law</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This Supplemental Indenture and the Notes shall be governed by and construed in accordance with the laws of the State of New York. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;408 <U>Waiver of Jury Trial</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">EACH OF THE COMPANY, THE TRUSTEE AND EACH HOLDER OF A SECURITY BY ITS ACCEPTANCE THEREOF, HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT
PERMITTED BY APPLICABLE LAW, ANY AND ALL RIGHT IT MAY HAVE TO TRIAL BY JURY IN ANY LEGAL PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS SUPPLEMENTAL INDENTURE, THE SECURITIES, THE INDENTURE OR THE TRANSACTIONS CONTEMPLATED
HEREBY OR THEREBY. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;409 <U>Counterparts</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This Supplemental Indenture may be executed in several counterparts, each of which shall be an original and all of which shall constitute but
one and the same instrument. Each signed copy shall be an original, but all of them together represent the same agreement. The exchange of copies of this Supplemental Indenture and of signature pages by facsimile or PDF transmission shall constitute
effective execution and delivery of this Supplemental Indenture as to the parties hereto and may be used in lieu of the original Supplemental Indenture for all purposes. Signatures of the parties hereto transmitted by facsimile or PDF shall be
deemed to be their original signatures for all purposes. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">5 </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Section&nbsp;410 <U>Trustee</U>. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Trustee shall not be responsible for and makes no representation as to the validity, sufficiency or adequacy of this Supplemental
Indenture, and it shall not be responsible for any statement of the Company in this Supplemental Indenture. The Trustee makes no representations with respect to the effectiveness or adequacy of this Supplemental Indenture. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><I>[signature page follows] </I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">6 </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly
executed all as of the day and year first above written. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
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<TD></TD>
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<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="5">CULLEN/FROST BANKERS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="4"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-bottom:1pt; margin-top:0pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Jerry Salinas</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Jerry Salinas</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Group Executive Vice President and Chief Financial Officer</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16" COLSPAN="5"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="5"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">THE BANK OF NEW YORK MELLON,</P> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">as
Trustee</P></TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ Francine Kincaid</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Name:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Francine Kincaid</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Title:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">Vice President</P></TD></TR>
</TABLE></DIV>

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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit A </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>FORM OF NOTE </B></P>

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<TD VALIGN="top">Registered No. <B>1</B></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="right"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right">CUSIP NO. 229899 AB5</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman" ALIGN="right">ISIN US229899AB55</P></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">THIS SECURITY IS AN UNSECURED SUBORDINATED DEBT OBLIGA-TION OF CULLEN/FROST BANKERS, INC. THIS SECURITY IS NOT
A DEPOSIT OR SAVINGS ACCOUNT AND IS NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENTAL AGENCY OR INSTRUMENTALITY. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY
OR A NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOS-ITARY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTAN-CES DESCRIBED IN THE INDENTURE. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED
REP-RESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK COR-PORATION (&#147;DTC&#148;), TO CULLEN/FROST BANKERS, INC. OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTI-FICATE ISSUED IS REGISTERED IN THE NAME OF
CEDE&nbsp;&amp; CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE&nbsp;&amp; CO. OR TO SUCH OTHER EN-TITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE
OR OTHER USE HEREOF FOR VALUE OR OTHER-WISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGIS-TERED OWNER HEREOF, CEDE&nbsp;&amp; CO., HAS AN INTEREST HEREIN. </P>
<P STYLE="margin-top:24pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>CULLEN/FROST BANKERS, INC. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>4.500% Subordinated Notes Due 2027 </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>$100,000,000 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>Cullen/Frost Bankers, Inc., a corporation duly organized and existing under the laws of the State of Texas (herein called the
&#147;Company&#148;, which term includes any successor Person under the Indenture hereinafter referred to), for value received, hereby promises to pay to Cede&nbsp;&amp; Co., or registered assigns, the principal sum of One Hundred Million Dollars
($100,000,000) on March&nbsp;17, 2027 (the &#147;Maturity Date&#148;). The Company further promises to pay interest on said principal sum from and including March&nbsp;17, 2017, or from the most recent Interest Payment Date on which interest has
been paid or duly provided for, semi-annually in arrears on March&nbsp;17 and September&nbsp;17 of each year (each such date, an &#147;Interest Payment Date&#148;), commencing September&nbsp;17, 2017, at the rate of 4.500%&nbsp;<I>per annum</I>
(calculated in the basis of a 360 day year having twelve 30-day months), until the principal hereof is paid or duly provided for or made available for payment. Any such installment of interest that is overdue shall also bear interest at the rate of
4.500%<I>&nbsp;per annum</I> (to the extent that the payment of such interest shall be legally enforceable), from the date any such overdue amount first becomes due until it is paid or made available for payment. The term &#147;interest&#148; refers
not only to regularly scheduled interest payments but also to interest on interest payments not paid on the applicable Interest Payment Date.<I> </I></P>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Notwithstanding anything to the contrary in the Indenture, for purposes hereof, the following
terms have the following meanings: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">&#147;Business Day&#148; means any day that is not a Saturday or Sunday, and that is not a day on
which banking institutions are generally authorized or obligated by law, regulation or executive order to close in The City of New York. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">&#147;Regular Record Date&#148; means the immediately preceding February 28 for an Interest Payment Date falling on March&nbsp;17 or the
immediately preceding August 31 for an Interest Payment Date falling on September 17. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The interest so payable, and punctually paid or
duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the Regular Record Date for such
interest. Any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security (or one or more Predecessor
Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to
such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such
exchange, all as more fully provided in said Indenture. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">If an Interest Payment Date is not a Business Day, the Company shall pay interest
on the next day that is a Business Day, with the same force and effect as if made on the Interest Payment Date, and without any additional interest or other payment with respect to the delay. If the Maturity Date, or, if earlier, the Redemption
Date, falls on a day that is not a Business Day, the payment of principal and interest, if any, shall be made on the next day that is a Business Day, with the same force and effect as if made on such Maturity Date or earlier Redemption Date, and
without any additional interest or other payment with respect to the delay. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman"><I></I>Payment of the principal of (and premium, if any) and
any such interest on this Security will be made at the office or agency of the Company maintained for that purpose in the Borough of Manhattan, The City of New York, in such coin or currency of the United States of America as at the time of payment
is legal tender for payment of public and private debts; <I>provided, however</I>, that at the option of the Company payment of interest (other than any interest payable at Maturity) will be made (i)&nbsp;by check mailed to the address of the Person
entitled thereto as such address shall appear in the Securities Register or (ii)&nbsp;by wire transfer in immediately available funds at such place and to such account as may be designated by the Person entitled thereto as specified in the
Securities Register; <I>provided, further</I>, that any such payment and any such interest on the Securities beneficially held that are represented by this Global Security, and all transfers and deliveries of such Securities shall be made to the
Depositary, which shall initially be the Depository Trust Company, or its nominee, as the case may be, as the Holder of this Global Security, in accordance with the Depositary&#146;s procedures.<I> </I></P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-2- </P>


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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Reference is hereby made to the further provisions of this Security set forth on the reverse
hereof, which further provisions shall for all purposes have the same effect as if set forth at this place. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Unless the certificate of
authentication hereon has been executed by the Trustee referred to on the reverse hereof by manual signature, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-3- </P>


<p Style='page-break-before:always'>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">I<SMALL>N</SMALL> W<SMALL>ITNESS</SMALL> W<SMALL>HEREOF</SMALL>, the Company has caused this
instrument to be duly executed under its corporate seal. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Dated: </P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="6%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD WIDTH="92%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">CULLEN/FROST BANKERS, INC.</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name: Jerry Salinas</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title: Group Executive Vice</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;President and Chief Financial</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Officer</TD></TR>
</TABLE></DIV> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">[seal] </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="12%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="87%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Attest:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name: Stan McCormick</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title: Executive Vice President,</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Corporate Counsel and</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Secretary</TD></TR>
</TABLE></DIV> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This is one of the Securities of the series designated therein referred to in the within-mentioned
Indenture. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="40%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="6%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD WIDTH="92%"></TD></TR>


<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">THE BANK OF NEW YORK</P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman">MELLON,</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" COLSPAN="3">As Trustee</TD></TR>
<TR STYLE="font-size:1pt">
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">&nbsp;</P></TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Name:</TD></TR>
<TR STYLE="page-break-inside:avoid ; font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom">Title:</TD></TR>
</TABLE></DIV>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-4- </P>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">[Reverse of Security] </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This Security is one of a duly authorized issue of securities of the Company (herein called the &#147;Securities&#148;), issued and to be
issued in one or more series under an Indenture, dated as of February&nbsp;15, 2007 (herein called the Indenture, which term shall have the meaning assigned to it in such instrument), between the Company and The Bank of New York, as Trustee (herein
called the &#147;Trustee&#148;, which term includes any successor trustee under the Indenture), and reference is hereby made to the Indenture and all indentures supplemental thereto for a statement of the respective rights, limitations of rights,
duties and immunities thereunder of the Company, the Trustee, the holders of Senior Indebtedness and the Holders of the Securities and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of
the series designated on the face hereof, initially limited in aggregate principal amount to U.S. $100,000,000. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Securities of this
series are subject to redemption upon not less than 30 days&#146; nor more than 60 days&#146; notice by mail and subject to any regulatory approvals that may be required, at any time or from time to time on or after February&nbsp;17, 2027, as a
whole or in part, at the election of the Company, at a Redemption Price equal to 100% of the principal amount, together in the case of any such redemption with accrued interest to the Redemption Date, but interest installments whose Stated Maturity
is on or prior to such Redemption Date will be payable to the Holders of such Securities, or one or more Predecessor Securities, of record at the close of business on the relevant Record Dates referred to on the face hereof, all as provided in the
Indenture. Any such redemption will be subject to the prior approval of the Board of Governors of the Federal Reserve System (&#147;FRB&#148;). </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">No sinking fund will be provided with respect to the Securities of this series. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In the event of redemption of this Security in part only, a new Security or Securities of this series and of like tenor for the unredeemed
portion hereof will be issued in the name of the Holder hereof upon the cancellation hereof. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The indebtedness evidenced by this Security
is, to the extent provided in the Indenture, subordinate and subject in right of payment to the prior payment in full of all Senior Indebtedness, and this Security is issued subject to the provisions of the Indenture with respect thereto. Each
Holder of this Security, by accepting the same, (a)&nbsp;agrees to and shall be bound by such provisions, (b)&nbsp;authorizes and directs the Trustee on his or her behalf to take such actions as may be necessary or appropriate to effectuate the
subordination so provided and (c)&nbsp;appoints the Trustee his or her attorney-in-fact for any and all such purposes. Each Holder hereof, by his or her acceptance hereof, waives all notice of the acceptance of the subordination provisions contained
herein and in the Indenture by each holder of Senior Indebtedness, whether now outstanding or hereafter created, incurred, assumed or guaranteed, and waives reliance by each such holder upon said provisions. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">If an Event of Default with respect to Securities of this series shall occur and be continuing, the principal of the Securities of this series
may be declared due and payable in the manner and with the effect provided in the Indenture. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-5- </P>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the
modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Company and the Trustee with the consent of the Holders of 66 <SUP
STYLE="font-size:85%; vertical-align:top">2</SUP>/<SUB STYLE="font-size:85%; vertical-align:bottom">3</SUB>% in principal amount of the Securities at the time Outstanding of each series to be affected. The Indenture also contains provisions
permitting the Holders of specified percentages in principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of
the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Security and of any
Security issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">As provided in and subject to the provisions of the Indenture, the Holder of this Security shall not have the right to institute any
proceeding with respect to the Indenture or for the appointment of a receiver or trustee or for any other remedy thereunder, unless such Holder shall have previously given the Trustee written notice of a continuing Default with respect to the
Securities of this series, the Holders of not less than 25% in principal amount of the Securities of this series at the time Outstanding shall have made written request to the Trustee to institute proceedings in respect of such Default as Trustee
and offered the Trustee indemnity reasonably satisfactory to it, and the Trustee shall not have received from the Holders of a majority in principal amount of Securities of this series at the time Outstanding a direction inconsistent with such
request, and shall have failed to institute any such proceeding, for 60 days after receipt of such notice, request and offer of indemnity. The foregoing shall not apply to any suit instituted by the Holder of this Security for the enforcement of any
payment of principal hereof or any premium or interest hereon on or after the respective due dates expressed herein. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">No reference herein
to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the principal of and any premium and interest on this Security at the times,
place and rate, and in the coin or currency, herein prescribed. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Security is registrable in the Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Company maintained under Section&nbsp;1002 of the Indenture for such
purpose, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing, and thereupon one or more
new Securities of this series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The Securities of this series are issuable only in registered form without coupons in denominations of $1,000 and any integral multiple
thereof. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series and of like tenor of a different authorized
denomination, as requested by the Holder surrendering the same. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-6- </P>


<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">No service charge shall be made for any such registration of transfer or exchange, but the
Company may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Prior to
due presentment of this Security for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not
this Security be overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the contrary. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">This
Security shall be governed by and construed in accordance with the laws of the State of New York. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">All terms used in this Security which
are defined in the Indenture shall have the meanings assigned to them in the Indenture. </P>
 <p STYLE="margin-top:0pt;margin-bottom:0pt ; font-size:8pt">&nbsp;</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center">-7- </P>

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<TYPE>EX-5.1
<SEQUENCE>3
<FILENAME>d345021dex51.htm
<DESCRIPTION>EX-5.1
<TEXT>
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 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right"><B>Exhibit 5.1 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="right">March&nbsp;17, 2017 </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Cullen/Frost Bankers, Inc.
</P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">100 West Houston Street </P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">San Antonio, Texas 78205 </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman">Ladies and Gentlemen: </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">In connection with the
registration under the Securities Act of 1933 (the &#147;<I>Act</I>&#148;) of $100,000,000 aggregate principal amount of 4.500% Subordinated Notes due March&nbsp;17, 2027 (the &#147;<I>Notes</I>&#148;) of Cullen/Frost Bankers, Inc., a Texas
corporation (the &#147;<I>Company</I>&#148;), I, as Executive Vice President, Corporate Counsel and Secretary of the Company, have examined such corporate records, certificates and other documents, and such questions of Texas law, as I have
considered necessary or appropriate for the purposes of this opinion. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Upon the basis of such examination, I advise you that, in my
opinion, the Notes have been validly issued and are fully paid and nonassessable. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The foregoing opinion is limited to the laws of the
State of Texas, and I am expressing no opinion as to the effect of the laws of any other jurisdiction. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">I have relied as to certain
matters on information obtained from public officials, officers of the Company and other sources believed by me to be responsible and have assumed the legal capacity of all natural persons and that all signatures on documents examined by me were
genuine, all documents submitted to me as originals are authentic and all documents submitted to me as certified or photostatic copies conform with the original copies of such documents. </P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">I hereby consent to the filing of this opinion as an exhibit to the registration statement relating to the Notes and to the reference to me
under the heading &#147;Validity of the Securities&#148; in the prospectus supplement relating to the Notes. In giving such consent, I do not thereby admit that I am in the category of persons whose consent is required under Section&nbsp;7 of the
Act. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><DIV ALIGN="right">
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<TD VALIGN="top">Very truly yours,</TD></TR>
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<TD VALIGN="top">/s/ Stanley E. McCormick</TD></TR>
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<TD VALIGN="top">Executive Vice President Corporate Counsel and Secretary</TD></TR>
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