GUARANTEE AGREEMENT

Exhibit 4.5

GUARANTEE AGREEMENT

by and between

WELLS FARGO & COMPANY

as Guarantor

and

THE BANK OF NEW YORK MELLON TRUST COMPANY, NATIONAL ASSOCIATION

as Guarantee Trustee

relating to

WELLS FARGO CAPITAL XIV

Dated as of August 19, 2008

TABLE OF CONTENTS

i

ii

GUARANTEE AGREEMENT, dated as of August 19, 2008, between WELLS FARGO & COMPANY, a Delaware corporation (the “ Guarantor ”), having its principal office at 420 Montgomery Street, San Francisco, California 94163, and THE BANK OF NEW YORK MELLON TRUST COMPANY, NATIONAL ASSOCIATION, as trustee (the “ Guarantee Trustee ”), for the benefit of the Holders (as defined herein) from time to time of the Capital Securities (as defined herein) of WELLS FARGO CAPITAL XIV, a Delaware statutory trust (the “ Issuer Trust ”).

RECITALS

WHEREAS, pursuant to an Amended and Restated Declaration of Trust and Trust Agreement, of even date herewith (the “ Trust Agreement ”), among Wells Fargo & Company, as Depositor, the Property Trustee, the Delaware Trustee and the Administrative Trustees (each as named therein) and the holders from time to time of undivided beneficial interests in the assets of the Issuer Trust, the Issuer Trust is issuing $690,000,000 aggregate Liquidation Amount (as defined in the Trust Agreement) of its 8.625% Enhanced Trust Preferred Securities (Enhanced T RU PS ^® ) (liquidation amount $25 per capital security) (the “ Capital Securities ”), representing preferred undivided beneficial interests in the assets of the Issuer Trust and having the terms set forth in the Trust Agreement; and

WHEREAS, the Capital Securities will be issued by the Issuer Trust, and the proceeds thereof, together with the proceeds from the issuance of the Issuer Trust’s Common Securities (as defined herein), will be used to purchase the Debentures of the Guarantor, which Debentures will be deposited with The Bank of New York Mellon Trust Company, National Association, as Property Trustee under the Trust Agreement, as trust assets; and

WHEREAS, as an incentive for the Holders to purchase Capital Securities, the Guarantor desires irrevocably and unconditionally to agree, to the extent set forth herein, to pay to the Holders of the Capital Securities the Guarantee Payments (as defined herein) and to make certain other payments on the terms and conditions set forth herein.

NOW, THEREFORE, in consideration of the purchase of Capital Securities by each Holder, which purchase the Guarantor hereby acknowledges shall benefit the Guarantor, the Guarantor executes and delivers this Guarantee Agreement for the benefit of the Holders from time to time.

ARTICLE I

DEFINITIONS

Section 1.1. Definitions.

For all purposes of this Guarantee Agreement, except as otherwise expressly provided or unless the context otherwise requires:

(a) the terms defined in this Article have the meanings assigned to them in this Article, and include the plural as well as the singular;

(b) all other terms used herein that are defined in the Trust Indenture Act, either directly or by reference therein, have the meanings assigned to them therein;

(c) the words “include,” “includes” and “including” shall be deemed to be followed by the phrase “without limitation”;

(d) all accounting terms used but not defined herein have the meanings assigned to them in accordance with United States generally accepted accounting principles;

(e) unless the context otherwise requires, any reference to an “Article” or a “Section” refers to an Article or a Section, as the case may be, of this Guarantee Agreement; and

(f) the words “hereby,” “herein,” “hereof” and “hereunder” and other words of similar import refer to this Guarantee Agreement as a whole and not to any particular Article, Section or other subdivision.

“ Affiliate ” of any specified Person means any other Person directly or indirectly controlling or controlled by or under direct or indirect common control with such specified Person. For the purposes of this definition, “control,” when used with respect to any specified Person, means the power to direct the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms “controlling” and “controlled” have meanings correlative to the foregoing.

“ Board of Directors ” means the board of directors of the Guarantor or any committee of the board of directors of the Guarantor, comprised of one or more members of the board of directors of the Guarantor or officers of the Guarantor, or both.

“ Capital Securities ” has the meaning specified in the recitals to this Guarantee Agreement.

“ Common Securities ” means the securities representing common undivided beneficial interests in the assets of the Issuer Trust.

“ Debentures ” shall have the meaning specified in the Trust Agreement.

“ Distributions ” shall have the meaning specified in the Trust Agreement.

“ Event of Default ” means (i) a default by the Guarantor in any of its payment obligations under this Guarantee Agreement or (ii) a default by the Guarantor in any other obligation hereunder that remains unremedied for 30 days.

“ Guarantee Agreement ” means this Guarantee Agreement, as modified, amended or supplemented from time to time.

“ Guarantee Payments ” means the following payments or distributions, without duplication, with respect to the Capital Securities, to the extent not paid or made by or on behalf of the Issuer Trust: (i) any accumulated and unpaid Distributions required to be paid on the Capital Securities, to the extent the Issuer Trust shall have funds on hand available therefor at such time; (ii) the Redemption Price with respect to any Capital Securities called for redemption by the Issuer Trust, to the extent the Issuer Trust shall have funds on hand available therefor at such time; and (iii) upon a voluntary or involuntary dissolution, winding-up or liquidation of the Issuer Trust, unless Debentures are distributed to the Holders, the lesser of (a) the Liquidation Distribution with respect to the Capital Securities, to the extent that the Issuer Trust shall have funds on hand available therefor at such time, and (b) the amount of assets of the Issuer Trust remaining available for distribution to Holders on liquidation of the Issuer Trust.

“ Guarantee Trustee ” means The Bank of New York Mellon Trust Company, National Association, solely in its capacity as Guarantee Trustee and not in its individual capacity, until a Successor Guarantee Trustee has been appointed and has accepted such appointment pursuant to the terms of this Guarantee Agreement, and thereafter means each such Successor Guarantee Trustee.

2

“ Guarantor ” has the meaning specified in the first paragraph of this Guarantee Agreement.

“ Holder ” means any Holder (as defined in the Trust Agreement) of any Capital Securities; provided, however , that in determining whether the holders of the requisite percentage of Capital Securities have given any request, notice, consent or waiver hereunder, “Holder” shall not include the Guarantor, the Guarantee Trustee, or any Affiliate of the Guarantor or the Guarantee Trustee.

“ Indemnified Person ” shall have the meaning specified in Section 3.3(c).

“ Indenture ” means the Indenture, dated as of August 1, 2005, between Wells Fargo & Company and The Bank of New York Mellon Trust Company, National Association (as successor in interest to J.P. Morgan Trust Company, National Association), as trustee, as supplemented by the Fifth Supplemental Indenture, dated as of August 19, 2008, between Wells Fargo & Company and The Bank of New York Mellon Trust Company, National Association, as trustee, as the same may be further modified, amended or supplemented from time to time.

“ Issuer Trust ” has the meaning specified in the first paragraph of this Guarantee Agreement.

“ Liquidation Distribution ” shall have the meaning specified in the Trust Agreement.

“ List of Holders ” has the meaning specified in Section 2.2(a).

“ Majority in Liquidation Amount of the Capital Securities ” means, except as provided by the Trust Indenture Act, Capital Securities representing more than 50% of the aggregate Liquidation Amount (as defined in the Trust Agreement) of all Capital Securities then Outstanding (as defined in the Trust Agreement).

“ Officers’ Certificate ” means, with respect to any Person, a certificate signed by the Chairman or a Vice Chairman of the Board of Directors of such Person or the President or a Vice President of such Person, and by the Treasurer, an Assistant Treasurer, the Secretary or an Assistant Secretary of such Person. Any Officers’ Certificate delivered with respect to compliance with a condition or covenant provided for in this Guarantee Agreement shall include:

(a) a statement by each officer signing the Officers’ Certificate that such officer has read the covenant or condition and the definitions relating thereto;

(b) a brief statement of the nature and scope of the examination or investigation undertaken by such officer in rendering the Officers’ Certificate;

(c) a statement that such officer has made such examination or investigation as, in such officer’s opinion, is necessary to enable such officer to express an informed opinion as to whether or not such covenant or condition has been complied with; and

(d) a statement as to whether, in the opinion of such officer, such condition or covenant has been complied with.

3

“ Person ” means a legal person, including any individual, corporation, estate, partnership, joint venture, association, joint stock company, company, limited liability company, trust, business trust, unincorporated association, or government or any agency or political subdivision thereof, or any other entity of whatever nature.

“ Redemption Price ” shall have the meaning specified in the Trust Agreement.

“ Responsible Officer ” means, with respect to the Guarantee Trustee, any officer within the corporate trust department of the Guarantee Trustee having direct responsibility for the administration of this Guarantee Agreement or to whom any corporate trust matter is referred because of such person’s knowledge of and familiarity with the particular subject.

“ Successor Guarantee Trustee ” means a successor Guarantee Trustee possessing the qualifications to act as Guarantee Trustee under Section 4.1.

“ Trust Agreement ” means the Amended and Restated Declaration of Trust and Trust Agreement of the Issuer Trust referred to in the recitals to this Guarantee Agreement, as modified, amended or supplemented from time to time.

“ Trust Indenture Act ” means the Trust Indenture Act of 1939 as in force at the date as of which this Guarantee Agreement was executed; provided, however , that in the event the Trust Indenture Act of 1939 is amended after such date, “Trust Indenture Act” means, to the extent required by any such amendment, the Trust Indenture Act of 1939 as so amended.

“ Vice President ,” when used with respect to the Guarantor, means any duly appointed vice president, whether or not designated by a number or a word or words added before or after the title “vice president.”

ARTICLE II

TRUST INDENTURE ACT

Section 2.1. Trust Indenture Act; Application.

Except as otherwise expressly provided herein, the Trust Indenture Act shall apply as a matter of contract to this Guarantee Agreement for purposes of interpretation, construction and defining the rights and obligations hereunder, and this Guarantee Agreement, the Guarantor and the Guarantee Trustee shall be deemed for all purposes hereof to be subject to and governed by the Trust Indenture Act to the same extent as would be the case if this Guarantee Agreement were qualified under the Trust Indenture Act on the date hereof. Except as otherwise expressly provided herein, if and to the extent that any provision of this Guarantee Agreement limits, qualifies or conflicts with the duties imposed by Sections 310 to 317, inclusive, of the Trust Indenture Act, such imposed duties shall control.

Section 2.2. List of Holders.

(a) The Guarantor shall furnish or cause to be furnished to the Guarantee Trustee (a) semiannually, on or before June 30 and December 31 of each year, a list, in such form as the Guarantee Trustee may reasonably require, of the names and addresses of the Holders (a “ List of Holders ”) as of a date not more than 15 days prior to the delivery thereof, and (b) at such other times as the Guarantee Trustee may request in writing, within 30 days after the receipt by the Guarantor of any

4

such request, a List of Holders as of a date not more than 15 days prior to the time such list is furnished, in each case to the extent such information is in the possession or control of the Guarantor and has not otherwise been received by the Guarantee Trustee in its capacity as such. The Guarantee Trustee may destroy any List of Holders previously given to it on receipt of a new List of Holders.

(b) The Guarantee Trustee shall comply with the requirements of Section 311(a), Section 311(b) and Section 312(b) of the Trust Indenture Act.

Section 2.3. Reports by the Guarantee Trustee.

Within 60 days after May 15 each year, commencing May 15, 2009, the Guarantee Trustee shall provide to the Holders such reports as are required by Section 313 of the Trust Indenture Act, if any, in the form and in the manner provided by Section 313 of the Trust Indenture Act. If this Guarantee Agreement shall have been qualified under the Trust Indenture Act, the Guarantee Trustee shall also comply with the requirements of Section 313(d) of the Trust Indenture Act.

Section 2.4. Periodic Reports to the Guarantee Trustee.

The Guarantor shall provide to the Guarantee Trustee and the Holders such documents, reports and information, if any, as required by Section 314 of the Trust Indenture Act and the compliance certificate required by Section 314 of the Trust Indenture Act, in the form, in the manner and at the times required by Section 314 of the Trust Indenture Act, provided that such documents, reports and information shall be required to be provided to the Securities and Exchange Commission only if this Guarantee Agreement shall have been qualified under the Trust Indenture Act.

Section 2.5. Evidence of Compliance with Conditions Precedent.

The Guarantor shall provide to the Guarantee Trustee such evidence of compliance with such conditions precedent, if any, provided for in this Guarantee Agreement that relate to any of the matters set forth in Section 314(c) of the Trust Indenture Act. Any certificate or opinion required to be given by an officer of the Guarantor pursuant to Section 314(c)(1) may be given in the form of an Officers’ Certificate.

Section 2.6. Events of Default; Waiver.

The Holders of at least a Majority in Liquidation Amount of the Capital Securities may, by vote, on behalf of the Holders of all the Capital Securities, waive any past default or Event of Default and its consequences. Upon such waiver, any such default or Event of Default shall cease to exist, and any default or Event of Default arising therefrom shall be deemed to have been cured, for every purpose of this Guarantee Agreement, but no such waiver shall extend to any subsequent or other default or Event of Default or impair any right consequent thereon.

Section 2.7. Event of Default; Notice.

(a) The Guarantee Trustee shall, within 90 days after the occurrence of an Event of Default known to the Guarantee Trustee, transmit by mail, first class postage prepaid, to the Holders, notice of any such Event of Default known to the Guarantee Trustee, unless such Event of Default has been cured before the giving of such notice, provided that , except in the case of a default in the payment of a Guarantee Payment, the Guarantee Trustee shall be protected in withholding such notice if and so long as the board of directors, the executive committee or a trust committee of directors and/or Responsible Officers of the Guarantee Trustee in good faith determines that the withholding of such notice is in the interests of the Holders.

5

(b) The Guarantee Trustee shall not be deemed to have knowledge of any Event of Default unless the Guarantee Trustee shall have received written notice, or a Responsible Officer charged with the administration of this Guarantee Agreement shall have obtained written notice, of such Event of Default.

Section 2.8. Conflicting Interests.

The Trust Agreement and the Indenture shall be deemed to be specifically described in this Guarantee Agreement for the purposes of clause (i) of the first proviso contained in Section 310(b) of the Trust Indenture Act.

ARTICLE III

POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

Section 3.1. Powers and Duties of the Guarantee Trustee.

(a) This Guarantee Agreement shall be held by the Guarantee Trustee for the benefit of the Holders, and the Guarantee Trustee shall not transfer this Guarantee Agreement to any Person except to a Successor Guarantee Trustee on acceptance by such Successor Guarantee Trustee of its appointment to act as Guarantee Trustee hereunder. The right, title and interest of the Guarantee Trustee, as such, hereunder shall automatically vest in any Successor Guarantee Trustee, upon acceptance by such Successor Guarantee Trustee of its appointment hereunder, and such vesting and cessation of title shall be effective whether or not conveyancing documents have been execute