UNDERWRITING AGREEMENT

Exhibit 1.1

LINCOLN NATIONAL CORPORATION

Underwriting Agreement

$500,000,000 6.05% Capital Securities due 2067

Ladies and Gentlemen:

Lincoln National Corporation, an Indiana corporation (the “ Company ”), proposes to issue and sell to the firms named in Schedule I hereto (the “ Underwriters ” with respect to the securities specified herein), for whom you are acting as representatives (the “ Representatives ”), the principal amount of its securities or aggregate number of shares identified in Schedule II hereto (the “ Securities ”), to be issued under the indenture specified in Schedule II hereto (the “ Indenture ”) between the Company and the Trustee identified in such Schedule (the “ Trustee ”).

The Company has prepared and filed with the Securities and Exchange Commission (the “ Commission ”) under the Securities Act of 1933, as amended (the “ Act ”), an “automatic shelf registration statement” as defined under Rule 405 under the Act on Form S-3 (file number 333-132416), relating to securities (the “ Shelf Securities ”), including the Securities, to be issued from time to time by the Company. Such registration statement, including the exhibits thereto and the other information and documents deemed pursuant to Rule 430B under the Act to be part thereof as amended to (and including) the date of this Agreement, but excluding any Statement of Eligibility (Form T-1) under the Trust Indenture Act of 1939, as amended (the “ Trust Indenture Act ”), is hereinafter referred to as the “ Registration Statement ”. The term “ Basic Prospectus ” means the prospectus, dated March 14, 2006, included in the Registration Statement. The Company proposes to file with the Commission pursuant to Rule 424 under the Act a supplement or supplements to the Basic Prospectus relating to the Securities and the plan of distribution thereof and has previously advised you of all further information (financial and other) with respect to the Company to be set forth therein. The term “ Prospectus ” means the Basic Prospectus, as supplemented by the prospectus supplement including pricing information specifically relating to the Securities in the form filed pursuant to Rule 424(b) under the Act (or in the form first made available to the Underwriters by the Company to meet

requests of purchasers pursuant to Rule 173 under the Act) and the term “ preliminary prospectus ” means any preliminary form of the Prospectus including the “subject to completion” legend required by Item 501(b)(10) under Regulation S-K under the Act which has heretofore been filed pursuant to Rule 424 under the Act. The term “ Time of Sale Prospectus ” means the Basic Prospectus, as supplemented by the preliminary prospectus last filed before the Applicable Time (as defined below) pursuant to Rule 424 under the Act relating specifically to the Securities, as of 4:50 P.M. on March 8, 2007 (the “ Applicable Time ”), together with the free writing prospectuses, if any, identified in Schedule III hereto, and the term “ free writing prospectus ” has the meaning set forth in Rule 405 under the Act. As used herein, the terms “Registration Statement,” “Basic Prospectus,” “preliminary prospectus,” “Time of Sale Prospectus” and “Prospectus” shall include the documents, if any, incorporated by reference therein. The terms “supplement,” “amendment,” and “amend” as used herein with respect to the Registration Statement, the Basic Prospectus, any preliminary prospectus, the Time of Sale Prospectus, the Prospectus or any free writing prospectus shall be deemed to refer to and include the filing of any free writing prospectus and the filing of any document under the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”) that are deemed to be incorporated therein by reference.

1. Representations and Warranties . The Company represents and warrants to, and agrees with, each Underwriter that:

(a) The Company meets the requirements for use of an “automatic shelf registration statement” as defined under Rule 405 under the Act, on Form S-3, and has filed with the Commission the Registration Statement, which has become effective. The Registration Statement meets the requirements set forth in Rule 415(a)(1)(x) under the Act and complies in all other material respects with said Rule.

(b) (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) each part of the Registration Statement, when such part became effective, did not contain, and each such part, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement as of the date hereof and as of the Closing Date (as defined in Section 3) does not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iv) the Registration Statement and the Prospectus comply, and as amended or supplemented, if applicable, will comply, and the Indenture will comply, in all material respects with the Act, the Trust Indenture Act of 1939, as amended (the “ Trust Indenture Act ”), and the Exchange Act and the applicable rules and regulations

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thereunder, (v) each free writing prospectus filed by the Company, as of its issue date and at all subsequent times through the completion of the public offer and sale of the Securities, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement or the Prospectus, including any document incorporated by reference therein and any preliminary or other prospectus deemed to be a part thereof that has not been superseded or modified, as they exist as of the time of filing of such free writing prospectus, (vi) the Time of Sale Prospectus does not, and at the time of each sale of the Securities in connection with the offering and at the Closing Date, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, and (vii) the Prospectus, as of its date and as of the Closing Date, does not and will not contain and, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus as of its date and the Closing Date based upon information relating to any Underwriter or any underwriting arrangements furnished to the Company in writing by such Underwriter through the Representatives expressly for use therein.

(c) The financial statements of the Company and its consolidated subsidiaries included in the Registration Statement fairly present the financial condition and results of operations of the Company and its consolidated subsidiaries as of the dates indicated and the results of operations and changes in financial position for the periods therein specified; neither the Company nor any of its consolidated subsidiaries has sustained since the date of the latest audited financial statements included or incorporated by reference in the Prospectus or Time of Sale Prospectus any material loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, otherwise than as set forth or contemplated in the Prospectus and Time of Sale Prospectus; and, since the respective dates as of which information is given in the Registration Statement and the Basic Prospectus, there has not been any material change in the capital stock (other than issuances of common stock upon the exercise of outstanding employee stock options or pursuant to existing employee compensation plans) or long-term debt of the Company or any of its subsidiaries or any material adverse change, or any development involving a prospective material adverse change, in the condition (financial or other), earnings, business or properties of the Company and its consolidated subsidiaries taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth or contemplated in the Prospectus and Time of Sale Prospectus.

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(d) At the time of filing the Registration Statement, at the time of the most recent amendment thereto for the purposes of complying with Section 10(a)(3) of the Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Section 13 or 15(d) of the Exchange Act or form of prospectus), and at the time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c) under the Act) made any offer relating to the Securities in reliance on the exemption of Rule 163 under the Act, the Company was a “well-known seasoned issuer” as defined in Rule 405 under the Act.

(e) The Company is not an “ineligible issuer” in connection with the offering pursuant to Rules 164, 405 and 433 under the Act. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Act has been, or will be, filed with the Commission in accordance with the requirements of the Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Act or that was prepared by or on behalf of or used by the Company complies or will comply in all material respects with the requirements of the Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule III hereto, and electronic road shows each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

(f) The Company has been duly incorporated and is validly existing as a corporation under the laws of the jurisdiction of its incorporation, with power and authority (corporate and other) to own, lease and operate its properties and to conduct its business as described in the Basic Prospectus and has been duly qualified as a foreign corporation for the transaction of business and is in good standing under the laws of each other jurisdiction in which it owns or leases properties, or conducts any business, so as to require such qualification, or is subject to no material liability or disability by reason of the failure to be qualified in any such jurisdiction; and each subsidiary of the Company organized under the laws of the United States representing 10% or more of the consolidated earnings before income taxes and extraordinary items or consolidated total assets of the Company (each such subsidiary as set forth in Schedule IV hereto, a “ Significant Subsidiary ”) has been duly incorporated and is validly existing as a corporation under the laws of its jurisdiction of incorporation except where the failure to be so qualified would not have a material adverse effect on the Company and the subsidiaries taken as a whole.

(g) The Company has an authorized capitalization as set forth in the Time of Sale Prospectus and the Prospectus, and all of the issued shares of capital stock of the Company have been duly and validly authorized and issued and are fully paid and non-assessable.

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(h) The Securities have been duly authorized, and, when the Securities are issued and delivered pursuant to this Agreement, such Securities will have been duly executed, authenticated, issued and delivered (and, in the case of Securities representing capital stock of the Company, will be fully paid and nonassessable) and will constitute valid and legally binding obligations of the Company entitled to the benefits provided by the Indenture; such Indenture has been duly qualified under the Trust Indenture Act and, at the Closing Date (as hereinafter defined) for any Securities, such Securities will constitute valid and legally binding obligations of the Company, enforceable in accordance with their respective terms, subject, as to enforcement, to bankruptcy, insolvency, fraudulent transfer, moratorium and other similar laws relating to or affecting creditors’ rights generally and to general principles of equity.

(i) The issue and sale of the Securities and the compliance by the Company with all of the provisions of the Securities, this Agreement and the Indenture, and the consummation of the transactions herein and therein contemplated will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, any material indenture, mortgage, deed of trust, loan agreement or other material agreement or instrument to which the Company or any subsidiary is a party or by which the Company or any subsidiary is bound or to which any of the property or assets of the Company or any subsidiary is subject, except for such conflicts, breaches, violations or defaults as would not, individually or in the aggregate, have a material adverse effect on the consolidated financial position of the Company and its subsidiaries taken as a whole, or the consummation by the Company of the transactions contemplated by this Agreement and the Indenture, nor will such action result in any violation of the provisions of (i) the articles of incorporation or bylaws of the Company or any Significant Subsidiary or (ii) any statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over the Company, any subsidiary or any of its respective properties, except, in the case of (ii) above, for such violations that would not, individually or in the aggregate, have a material adverse effect on the consolidated financial position of the Company and its subsidiaries taken as a whole or the consummation by the Company of the transactions contemplated by this Agreement and the Indenture; and no consent, approval, authorization, order, registration or qualification of or with any such court or governmental agency or body is required for the issue and sale of the Securities or the consummation by the Company of the transactions contemplated by the Securities, this Agreement and the Indenture, except such as have been, or will have been prior to the time of delivery, obtained under the Act and in the case of Securities to be issued under an Indenture, the Trust Indenture Act and such consents, approvals, authorizations, registrations or qualifications as may be required under state securities or Blue Sky laws in connection with the purchase and distribution of the Securities by the Underwriters.

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(j) Other than as set forth in the Prospectus and the Time of Sale Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries is a party or of which any property of the Company or any of its subsidiaries is the subject which would individually or in the aggregate be reasonably likely to have a material adverse effect on the consolidated financial position, stockholders’ equity or results of operations of the Company and its subsidiaries taken as a whole; and, to the best of the Company’s knowledge, no such proceedings are threatened or contemplated by governmental authorities or threatened by others.

(k) The Company and its subsidiaries own or possess, or can acquire on reasonable terms, all material trademarks, service marks and trade names necessary to conduct the business now operated by them, and neither the Company nor any of its subsidiaries has received any notice of infringement of or conflict with asserted rights of others with respect to any trademarks, service marks or trade names that singly or in the aggregate, would be reasonably likely to materially adversely affect the conduct of the business, operations, financial condition or income of the Company and its subsidiaries considered as a whole.

(l) To the best of the Company’s knowledge and belief, the Company has complied in all material respects with, and the conduct of its business and the conduct of business by its subsidiaries does not violate in any material respect, any statute, law, regulation, rule, order or directive of any federal, state or local governmental authority applicable to the Company and its subsidiaries.

2. Purchase and Sale . Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to each Underwriter, and each Underwriter agrees, severally and not jointly, to purchase from the Company, at the purchase price set forth in Schedule II hereto the principal amount or number of shares of the Securities set forth opposite such Underwriter’s name in Schedule I hereto.

3. Delivery and Payment . Securities to be purchased by each Underwriter hereunder, in definitive form to the extent practicable, and in such authorized denominations and registered in such names as the Representatives may request upon at least forty-eight hours’ prior notice to the Company, shall be delivered by or on behalf of the Company to the Representatives for the account of such Underwriter at the office of Sullivan & Cromwell LLP, on the date and at the time specified in Schedule II hereto (or such later date not later than five business days after such specified date as the Representatives shall designate), which date and time may be postponed by agreement between the Representatives and the Company or as provided in Section 8 hereof (such date and time of delivery and payment for the Securities being herein called the “ Closing Date ”). Delivery of the Securities shall be made to the

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Underwriters for the respective accounts of the several Underwriters against payment by the several Representatives of the purchase price thereof in Federal (same day) funds by official bank check or checks to or upon the order of the Company or by wire transfer to an account specified by the Company, checks payable in New York Clearing House (next day) funds or as otherwise set forth in Schedule II.

The Company agrees to have the Securities available for inspection, checking and packaging by the Underwriters in New York, New York, not later than 1:00 PM on the business day prior to the Closing Date.

4. Agreements .

(A) The Company agrees with the several Underwriters that:

(a) Prior to the termination of the offering of the Securities, the Company will not file any amendment or supplement to the Registration Statement, the Basic Prospectus or the Time of Sale Prospectus and will not provide additional information to the Commission relating to the Registration Statement, the Basic Prospectus or the Time of Sale Prospectus unless the Company has furnished you a copy for your review and provided you with a reasonable opportunity to comment on such proposed amendment, supplement, or information prior to filing or submitting the same and will not file any such proposed amendment or supplement and will not submit such additional information to which you reasonably object. The Company will promptly advise the Underwriters and will promptly confirm such advice in writing (i) when the Prospectus shall have been filed (or transmitted for filing) with the Commission pursuant to Rule 424, (ii) when any amendment to the Registration Statement relating to the Securities shall have been filed or become effective, (iii) of any request by the Commission for any amendment of the Registration Statement or amendment of or supplement to the Prospectus or for any additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any notice objecting to its use or the institution or threatening of any proceeding for such purpose and (v) of the receipt by the Company of any notification with respect to the suspension of the qualification of Securities for sale in any jurisdiction or the initiation or threatening of any proceeding for such purpose. The Company will use its best efforts to prevent the issuance of any such stop order and, if issued, to obtain as soon as possible the withdrawal thereof.

(b) As soon as practicable but in any event not later than eighteen months after the deemed effective date of the Registration Statement (as defined in Rule 158(c) under the Act), the Company will make generally available to its securityholders and to the Underwriters a consolidated earnings statement or statements of the Company and its

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subsidiaries (which need not be audited) which will satisfy the provisions of Section 11(a) of the Act and the rules and regulations thereunder (including at the option of the Company Rule 158 under the Act).

(c) The Company will furnish to the Underwriters and counsel for the Underwriters, without charge, a signed copy of the Registration Statement (including exhibits thereto and documents incorporated by reference) and to deliver to each of the Underwriters during the period mentioned in Section 4(A)(e) or 4(A)(f) below, as many copies of the Time of Sale Prospectus, the Prospectus, any documents incorporated therein by reference therein and any supplements and amendments thereto or to the Registration Statement as you may reasonably request.

(d) If the Time of Sale Prospectus is being used to solicit offers to buy the Securities at a time when the Prospectus is not yet available to prospective purchasers and any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Time of Sale Prospectus in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, or if any event shall occur or condition exist as a result of which the Time of Sale Prospectus conflicts with the information contained in the Registration Statement then on file, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Time of Sale Prospectus to comply with applicable law, forthwith to prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to any dealer upon request, either amendments or supplements to the Time of Sale Prospectus so that the statements in the Time of Sale Prospectus as so amended or supplemented will not, in the light of the circumstances under which they were made when delivered to a prospective purchaser, be misleading or so that the Time of Sale Prospectus, as amended or supplemented, will no longer conflict with the Registration Statement, or so that the Time of Sale Prospectus, as amended or supplemented, will comply with law.

(e) If, during such period after the first date of the public offering of the Securities as in the opinion of counsel for the Underwriters the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Act) is required by law to be delivered in connection with sales by an Underwriter or dealer, any event shall occur or condition exist as a result of which it is necessary to amend or supplement the Prospectus in order to make the statements therein, in the light of the circumstances under which they were made when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Act) is delivered to a purchaser, not misleading, or if, in the opinion of counsel for the Underwriters, it is necessary to amend or supplement the Prospectus to comply with applicable law, forthwith to prepare, file with the

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prepare, file with the Commission and furnish, at its own expense, to the Underwriters and to the dealers (whose names and addresses you will furnish to the Company) to which Securities may have been sold by you on behalf of the Underwriters and to any other dealers upon request, either amendments or supplements to the Prospectus so that the statements in the Prospectus as so amended or supplemented will not, in the light of the circumstances under which they were made when the Prospectus (or in lieu thereof the notice referred to in Rule 173(a) under the Act) is delivered to a purchaser, be misleading or so that the Prospectus, as amended or supplemented, will comply with law.

(f) The Company will promptly from time to time arrange for the qualification of the Securities for sale under the laws of such jurisdictions as the Representatives may reasonably designate, will maintain such qualifications in effect so long as required for the distribution of the Securities, and will arrange for the determination of the legality of the Securities for purchase by institutional investors; provided that in connection therewith the Company shall not be required to qualify as a foreign corporation or to execute a general consent to service of process in any jurisdiction or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise subject.

(g) Until the business day following the Closing Date, the Company will not, without the consent of the Underwriters, offer, sell or contract to sell, or announce the offering of, any debt securities (other than the March 8, 2007 offering by Lincoln National Corporation of $250,000,000 aggregate principal amount of its Floating Rate Senior Notes due 2010, the “ Senior Notes ”) covered by the Registration Statement or any other registration statement filed under the Act.

(h) The Company covenants and agrees with the several Underwriters that the Company will pay or cause to be paid the following: (i) the fees, disbursements and expenses of the Company’s counsel and accountants in connection with the registration of the Securities under the Act in connection with the preparation, printing and filing of the Registration Statement, any preliminary prospectus, the Time of Sale Prospectus, the Prospectus and any free writing prospectus prepared by or on behalf of, used by, or referred to by the Company and amendments and supplements to any of the foregoing, including all printing costs associated therewith, and the mailing and delivering of copies thereof to the Underwriters and dealers, in the quantities hereinabove specified; (ii) the cost of printing or producing any Agreement among Underwriters, this Agreement, any Blue Sky Survey, any Legal Investment Memoranda and any other documents in connection with the offering, purchase, sale and delivery of the Securities;(iii) all expenses in connection with the qualification of the Securities for offering and sale under state securities and Blue Sky laws as provided in Section 4(A)(e) hereof, including any reasonable fees and disbursements of counsel for the Underwriters in connection with such

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qualification and in connection with the Blue Sky and legal investment surveys; (iv) any fees charged by securities rating services for rating the Securities; (v) the cost of preparing the Securities; (vi) the fees and expenses of any Trustee, Paying Agent, or Transfer Agent and counsel for any such Trustee, Paying Agent or Transfer Agent in connection with the Securities; and (vii) all other costs and expenses incident to the performance of its obligations hereunder which are not otherwise specifically provided for in this Section. It is understood, however, that, except as provided in this Section, Section 6 and Section 7 hereof, the Underwriters will pay all of their own costs and expenses, including the fees of their counsel, transfer taxes on resale of any of the Securities by them, and any advertising expenses connected with any offers they may make.

(i) The Company will prepare the Prospectus as amended and supplemented in relation to the applicable Securities in a form approved by the Representatives and will file such Prospectus pursuant to Rule 424(b) under the Act not later than the Commission’s close of business on the second business day following the execution and delivery of this Agreement or, if applicable, such other time as may be required by Rule 424(b) and file promptly and simultaneously provide each Underwriter with a copy of all reports and any definitive proxy or information statements required to be filed by the Company with the Commission pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act for so long as the delivery (or in lieu thereof the notice referred to in Rule 173(a) under the Act) of a prospectus is required in connection with the offering or sale of such Securities. The Company will prepare a final term sheet, containing solely a description of the Securities, in a form approved by the Representatives and file such term sheet pursuant to Rule 433(d) under the Act within the time required by such Rule, and will file promptly all other material required to be filed by the Company with the Commission pursuant to Rule 433(d) under the Act.

(j) During a period of five years from the date of the Basic Prospectus and, provided the following are not available on the Commission’s EDGAR database, to furnish to the Representatives copies of all reports or other communications (financial or other) furnished to stockholders, and deliver to each Underwriter (i) as soon as they are available, copies of any reports and financial statements furnished to or filed with any national securities exchange on which the Securities or any class of securities of the Company is listed or, if requested by the Representatives, the Commission; and (ii) such additional information concerning the business and financial condition of the Company as the Representatives may from time to time reasonably request (provided such financial statements and reports are otherwise furnished to its stockholders generally or to the Commission).

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(k) The Company has given the Representatives notice of any filings made pursuant to the Exchange Act or the rules or regulations thereunder within 48 hours prior to the Applicable Time; the Compan