As filed with the Securities and Exchange Commission on June 21, 2012
================================================================================
                                                    1933 Act File No. 333-170228
                                                     1940 Act File No. 811-21727


                    U.S. SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM N-2

(Check appropriate box or boxes)

[ ]  REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
[ ]  Pre-Effective Amendment No. __
[X]  Post-Effective Amendment No. 1

and

[ ]  REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940
[X]  Amendment No. 6

                        First Trust Mortgage Income Fund
         Exact Name of Registrant as Specified in Declaration of Trust

           120 East Liberty Drive, Suite 400, Wheaton, Illinois 60187
 Address of Principal Executive Offices (Number, Street, City, State, Zip Code)

                                 (630) 765-8000
               Registrant's Telephone Number, including Area Code

                             W. Scott Jardine, Esq.
                          First Trust Portfolios L.P.
                       120 East Liberty Drive, Suite 400
                            Wheaton, Illinois 60187

 Name and Address (Number, Street, City, State, Zip Code) of Agent for Service

                          Copies of Communications to:

                               Eric F. Fess, Esq.
                             Chapman and Cutler LLP
                             111 West Monroe Street
                            Chicago, Illinois 60603

Approximate Date of Proposed Public Offering: From time to time after the
effective date of this Registration Statement

---------------

If any of the securities being registered on this form are offered on a delayed
or continuous basis in reliance on Rule 415 under the Securities Act of 1933,
other than securities offered in connection with a dividend reinvestment plan,
check the following box. [X]



      This Post-Effective Amendment No. 1 will become effective immediately upon
filing pursuant to Rule 462(d) under the Securities Act of 1933.

EXPLANATORY NOTE

      This Post-Effective Amendment No. 1 to the Registration Statement of a
Form N-2 (File No. 333-170228) of First Trust Mortgage Income Fund (the
"Registration Statement") is being filed pursuant to Rule 462(d) under the
Securities Act of 1933, as amended (the "Securities Act"), solely for the
purpose of filing exhibits to the Registration Statement. Accordingly, this
Post-Effective Amendment No. 1 consists only of a facing page, this explanatory
note and Part C of the Registration Statement on Form N-2 setting forth the
exhibits to the Registration Statement. This Post-Effective Amendment No. 1 does
not modify any other part of the Registration Statement. Pursuant to Rule 462(d)
under the Securities Act, this Post-Effective Amendment No. 1 shall become
effective immediately upon filing with the Securities and Exchange Commission.
The contents of the Registration Statement are hereby incorporated by reference.



                                      -2-





                           PART C - OTHER INFORMATION

Item 25: Financial Statements and Exhibits

1.    Financial Statements:

      The Registrant's audited financial statements, notes to the financial
statements and the report of independent public accounting firm thereon have
been incorporated into Part B of the Registration Statement by reference to
Registrant's Annual Report for the fiscal year ended October 31, 2011 contained
in its Form N-CSR, as described in the statement of additional information.


2.    Exhibits:

a.1   Declaration of Trust dated February 22, 2005.(1)

a.2   Amendment to Declaration of Trust to Change Principal Office.(4)

a.3   Amendment to Declaration of Trust to Change Name. (4)

b.    By-Laws of Fund.(3)

c.    None.

d.    Form of Share Certificate.(2)

e.    Terms and Conditions of the Dividend Reinvestment Plan.(2)

f.    None.

g.1   Investment Management Agreement between Registrant and First Trust
      Advisors L.P.(4)

g.2   Sub-Advisory Agreement between Registrant, First Trust Advisors L.P. and
      Brookfield Investment Management Inc.(4)

h.1   Form of Underwriting Agreement.**

h.2   Sales Agreement.*

i.    None.

j.    Custodian Services Agreement.(2)

k.1   Transfer Agency Services Agreement.(2)

k.2   Administration and Accounting Services Agreement.(2)

l.1   Opinion and consent of Chapman and Cutler LLP.*

l.2   Opinion and consent of Bingham McCutchen LLP.*


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m.    None.

n.    Consent of Independent Registered Public Accounting Firm.*

o.    None.

p.    Subscription Agreement between Registrant and First Trust Advisors L.P.(2)

q.    None.

r.1   Code of Ethics of Registrant.(3)

r.2   Code of Ethics of First Trust Portfolios L.P.(3)

r.3   Code of Ethics of First Trust Advisors L.P.(3)

r.4   Code of Ethics of Brookfield Investment Management Inc.(4)

s.    Powers of Attorney.(3)

--------------------------------------------------------------------------------

*    Filed herewith.

**   To be filed by amendment.

(1)  Filed on March 11, 2005 in Registrant's Registration Statement on Form N-2
     (File No. 333-123262) and incorporated herein by reference.

(2)  Filed on May 25, 2005 in Registrant's Amended Registration Statement on
     Form N-2/A (File No. 333-123262) and incorporated herein by reference.

(3)  Filed on October 29, 2010 in Registrant's Registration Statement on Form
     N-2 (File No. 333-170228) and incorporated herein by reference.

(4)  Filed on February 10, 2012 in Registrant's Registration Statement on Form
     N-2 (File No. 333-170228) and incorporated herein by reference.


Item 26: Marketing Arrangements

     Reference is made to the sales agreement for the Registrant's common shares
filed with this post-effective amendment to the Registrant's Registration
Statement, to the section entitled "Plan of Distribution" contained in
Registrant's Prospectus, filed herewith as Part A of Registrant's Registration
Statement, and to information contained under the section entitled "Plan of
Distribution" in any Prospectus Supplement to the Prospectus.


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Item 27:  Other Expenses of Issuance and Distribution

------------------------------------------------------- ------------------------
Securities and Exchange Commission Fees                 $   3,700
------------------------------------------------------- ------------------------
Financial Industry Regulatory Authority, Inc. Fees      $  10,000
------------------------------------------------------- ------------------------
Printing and Engraving Expenses                         $   5,000
------------------------------------------------------- ------------------------
Legal Fees                                              $ 100,000
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Listing Fees                                            $       -
------------------------------------------------------- ------------------------
Accounting Expenses                                     $  25,000
------------------------------------------------------- ------------------------
Blue Sky Filing Fees and Expenses                       $       -
------------------------------------------------------- ------------------------
Miscellaneous Expenses                                  $       -
------------------------------------------------------- ------------------------
Total                                                   $ 143,700
------------------------------------------------------- ------------------------


Item 28: Persons Controlled by or under Common Control with Registrant

    Not applicable.


Item 29:  Number of Holders of Securities

    At March 31, 2012

------------------------------------------------------- ------------------------
Title of Class                                          Number of Record Holders
------------------------------------------------------- ------------------------
Common Shares, $0.01 par value                          2,916
------------------------------------------------------- ------------------------






                                      -5-




Item 30: Indemnification

      Section 5.3 of the Registrant's Declaration of Trust provides as follows:

      Section 5.3. Mandatory Indemnification. (a) Subject to the exceptions and
limitations contained in paragraph (b) below:

            (i) every person who is or has been a Trustee or officer of the
      Trust (hereinafter referred to as a "Covered Person") shall be indemnified
      by the Trust against all liability and against all expenses reasonably
      incurred or paid by him or her in connection with any claim, action, suit
      or proceeding in which that individual becomes involved as a party or
      otherwise by virtue of being or having been a Trustee or officer and
      against amounts paid or incurred by that individual in the settlement
      thereof;

            (ii) the words "claim," "action," "suit" or "proceeding" shall apply
      to all claims, actions, suits or proceedings (civil, criminal,
      administrative or other, including appeals), actual or threatened; and the
      words "liability" and "expenses" shall include, without limitation,
      attorneys' fees, costs, judgments, amounts paid in settlement or
      compromise, fines, penalties and other liabilities.

      (b) No indemnification shall be provided hereunder to a Covered Person:

            (i) against any liability to the Trust or the Shareholders by reason
      of a final adjudication by the court or other body before which the
      proceeding was brought that the Covered Person engaged in willful
      misfeasance, bad faith, gross negligence or reckless disregard of the
      duties involved in the conduct of that individual's office;

            (ii) with respect to any matter as to which the Covered Person shall
      have been finally adjudicated not to have acted in good faith in the
      reasonable belief that that individual's action was in the best interest
      of the Trust; or

            (iii) in the event of a settlement involving a payment by a Trustee
      or officer or other disposition not involving a final adjudication as
      provided in paragraph (b)(i) or (b)(ii) above resulting in a payment by a
      Covered Person, unless there has been either a determination that such
      Covered Person did not engage in willful misfeasance, bad faith, gross
      negligence or reckless disregard of the duties involved in the conduct of
      that individual's office by the court or other body approving the
      settlement or other disposition or by a reasonable determination, based
      upon a review of readily available facts (as opposed to a full trial-type
      inquiry) that that individual did not engage in such conduct:

                  (A) by vote of a majority of the Disinterested Trustees (as
            defined below) acting on the matter (provided that a majority of the
            Disinterested Trustees then in office act on the matter); or

                  (B) by written opinion of (i) the then-current legal counsel
            to the Trustees who are not Interested Persons of the Trust or (ii)
            other legal counsel chosen by a majority of the Disinterested
            Trustees (or if there are no Disinterested Trustees with respect to
            the matter in question, by a majority of the Trustees who are not
            Interested Persons of the Trust) and determined by them in their
            reasonable judgment to be independent.

      (c) The rights of indemnification herein provided may be insured against
by policies maintained by the Trust, shall be severable, shall not affect any
other rights to which any Covered Person may now or hereafter be entitled, shall
continue as to a person who has ceased to be a Covered Person and shall inure to
the benefit of the heirs, executors and administrators of such person. Nothing
contained herein shall limit the Trust from entering into other insurance

                                      -6-


arrangements or affect any rights to indemnification to which Trust personnel,
including Covered Persons, may be entitled by contract or otherwise under law.

      (d) Expenses of preparation and presentation of a defense to any claim,
action, suit, or proceeding of the character described in paragraph (a) of this
Section 5.3 shall be advanced by the Trust prior to final disposition thereof
upon receipt of an undertaking by or on behalf of the Covered Person to repay
such amount if it is ultimately determined that the Covered Person is not
entitled to indemnification under this Section 5.3, provided that either:

            (i) such undertaking is secured by a surety bond or some other
      appropriate security or the Trust shall be insured against losses arising
      out of any such advances; or

            (ii) a majority of the Disinterested Trustees acting on the matter
      (provided that a majority of the Disinterested Trustees then in office act
      on the matter) or legal counsel meeting the requirement in Section
      5.3(b)(iii)(B) above in a written opinion, shall determine, based upon a
      review of readily available facts (as opposed to a full trial-type
      inquiry), that there is reason to believe that the Covered Person
      ultimately will be found entitled to indemnification.

      As used in this Section 5.3 a "Disinterested Trustee" is one (i) who is
not an "Interested Person" of the Trust (including anyone who has been exempted
from being an "Interested Person" by any rule, regulation or order of the
Commission), and (ii) against whom none of such actions, suits or other
proceedings or another action, suit or other proceeding on the same or similar
grounds is then or had been pending.

      (e) With respect to any such determination or opinion referred to in
clause (b)(iii) above or clause (d)(ii) above, a rebuttable presumption shall be
afforded that the Covered Person has not engaged in willful misfeasance, bad
faith, gross negligence or reckless disregard of the duties involved in the
conduct of such Covered Person's office in accordance with pronouncements of the
Commission.

Item 31: Business and Other Connections of Investment Advisers

The information in the Statement of Additional Information under the captions
"Management of the Fund--Trustees and Officers" and "Sub-Advisor" is hereby
incorporated by reference.

Item 32: Location of Accounts and Records.

First Trust Advisors L.P. maintains the Declaration of Trust, By-Laws, minutes
of trustees and shareholders meetings and contracts of the Registrant, all
advisory material of the investment adviser, all general and subsidiary ledgers,
journals, trial balances, records of all portfolio purchases and sales, and all
other required records.

Item 33: Management Services

Not applicable.


Item 34: Undertakings

1.    Registrant undertakes to suspend the offering of its shares until it
      amends its prospectus if (1) subsequent to the effective date of its
      Registration Statement, the net asset value declines more than 10 percent
      from its net asset value as of the effective date of the Registration
      Statement, or (2) the net asset value increases to an amount greater than
      its net proceeds as stated in the prospectus.

2.    Not applicable.

3.    Not applicable.


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4.    The Registrant undertakes (a) to file, during any period in which offers
      or sales are being made, a post-effective amendment to this Registration
      Statement:

      (1)   to include any prospectus required by Section 10(a)(3) of the
            Securities Act of 1933;

(2)   to reflect in the prospectus any facts or events arising after the
      effective date of the registration statement (or the most recent
      post-effective amendment thereof) which, individually or in the aggregate,
      represent a fundamental change in the information set forth in the
      registration statement; and

(3)   to include any material information with respect to the plan of
      distribution not previously disclosed in the registration statement or any
      material change to such information in the registration statement;

(b)   that, for the purpose of determining liability under the Securities Act of
      1933, each such post-effective amendment shall be deemed to be a new
      registration statement relating to the securities offered therein, and the
      offering of those securities at that time shall be deemed to be the
      initial bona fide offering thereof; and

(c)   to remove from registration by means of a post-effective amendment any of
      the securities being registered which remain unsold at the termination of
      the offering;

(d)   that, for the purpose of determining liability under the Securities Act of
      1933 to any purchaser, if the Registrant is subject to Rule 430C; each
      prospectus filed pursuant to Rule 497(b), (c), (d) or (e) under the
      Securities Act of 1933, shall be deemed to be part of and included in this
      Registration Statement as of the date it is first used after
      effectiveness. Provided, however, that no statement made in this
      Registration Statement or prospectus that is part of this registration
      statement or made in a document incorporated or deemed incorporated by
      reference into this registration statement or prospectus that is part of
      this registration statement will, as to a purchaser with a time of
      contract of sale prior to such first use, supercede or modify any
      statement that was made in this registration statement or prospectus that
      was part of this registration statement or made in any such document
      immediately prior to such date of first use;

(e)   that for the purpose of determining liability of the Registrant under the
      Securities Act of 1933 to any purchaser in the initial distribution of
      securities:

      The undersigned Registrant undertakes that in a primary offering of
      securities of the undersigned Registrant pursuant to this registration
      statement, regardless of the underwriting method used to sell the
      securities to the purchaser, if the securities are offered or sold to such
      purchaser by means of any of the following communications, the undersigned
      Registrant will be a seller to the purchaser and will be considered to
      offer or sell such securities to the purchaser:

(1)   any preliminary prospectus or prospectus of the undersigned Registrant
      relating to the offering required to be filed pursuant to Rule 497 under
      the Securities Act of 1933;

(2)   the portion of any advertisement pursuant to Rule 482 under the Securities
      Act of 1933 relating to the offering containing material information about
      the undersigned Registrant or its securities provided by or on behalf of
      the undersigned Registrant; and

(3)   any other communication that is an offer in the offering made by the
      undersigned Registrant to the purchaser.

5.    The Registrant undertakes that:

a.    For purposes of determining any liability under the Securities Act of
      1933, the information omitted from the form of prospectus filed as part of
      a registration statement in reliance upon Rule 430A and contained in the

                                      -8-


      form of prospectus filed by the Registrant under Rule 497(h) under the
      Securities Act of 1933 shall be deemed to be part of the Registration
      Statement as of the time it was declared effective; and

b.    For the purpose of determining any liability under the Securities Act of
      1933, each post-effective amendment that contains a form of prospectus
      shall be deemed to be a new registration statement relating to the
      securities offered therein, and the offering of the securities at that
      time shall be deemed to be the initial bona fide offering thereof.

6.    The Registrant undertakes to send by first class mail or other means
      designed to ensure equally prompt delivery, within two business days of
      receipt of a written or oral request, any Statement of Additional
      Information.

7.    Upon each issuance of securities pursuant to this Registration Statement,
      the Registrant undertakes to file a form of prospectus and/or prospectus
      supplement pursuant to Rule 497 and a post-effective amendment to the
      extent required by the Securities Act of 1933 and the rules and
      regulations thereunder, including, but not limited to a post-effective
      amendment pursuant to Rule 462(c) or Rule 462(d) under the Securities Act
      of 1933.


                                      -9-


                                   SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933 and the
Investment Company Act of 1940, the Registrant has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in this City of Wheaton, and State of Illinois, on the 21st day of
June, 2012.

                                        FIRST TRUST MORTGAGE INCOME FUND


                                        By: /s/ Mark R. Bradley
                                           -------------------------------------
                                           Mark R. Bradley
                                           President and Chief Executive Officer


     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the date indicated.


---------------------------------------  -------------------------------------  ------------------------------------
                                                                          
Signature                                Title                                  Date
---------------------------------------  -------------------------------------  ------------------------------------
By: /s/ Mark R. Bradley                  President and Chief Executive          June 21, 2012
   -----------------------------         Officer (Principal Executive
   Mark R. Bradley                       Officer)
---------------------------------------  -------------------------------------  ------------------------------------
By: /s/ James M. Dykas                   Chief Financial Officer, Chief         June 21, 2012
   -----------------------------         Accounting Officer and Treasurer
   James M. Dykas                        (Principal Financial and Accounting
                                         Officer)
---------------------------------------  -------------------------------------  ------------------------------------
   James A. Bowen(1)                     Chairman of the Board and Trustee  )
---------------------------------------  -------------------------------------
   Richard E. Erickson(1)                Trustee                            )    By: /s/ Scott Jardine
---------------------------------------  -------------------------------------       ----------------------------
   Thomas R. Kadlec(1)                   Trustee                            )        W. Scott Jardine
---------------------------------------  -------------------------------------       Attorney-In-Fact
   Robert F. Keith(1)                    Trustee                            )        June 21, 2012
---------------------------------------  -------------------------------------
   Niel B. Nielson(1)                    Trustee                            )
---------------------------------------  -------------------------------------  ------------------------------------


---------------

(1)   Original powers of attorney authorizing James A. Bowen, W. Scott Jardine,
      Kristi A. Maher and Eric F. Fess to execute Registrant's Registration
      Statement, and Amendments thereto, for each of the trustees of the
      Registrant on whose behalf this Registration Statement is filed, were
      previously executed and filed on October 29, 2010 as an Exhibit to the
      Registrant's Registration Statement on Form N-2 (File No. 333-170228).


                                      -10-


                               INDEX TO EXHIBITS

h.2.  Sales Agreement

l.1   Opinion and Consent of Chapman and Cutler LLP.

l.2   Opinion and Consent of Bingham McCutchen LLP.

n.    Consent of Independent Registered Accounting Firm.



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