As filed with the Securities and Exchange Commission on March 7, 2007

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                                            1933 Act Registration No. 333-140895
                                             1940 Act Registration No. 811-22019

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                    FORM N-1A

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

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940             [ ]
Amendment No. 1                                                             [X]


                   FIRST TRUST EXCHANGE-TRADED ALPHADEX(TM) FUND
               (Exact name of registrant as specified in charter)

                        1001 Warrenville Road, Suite 300
                              Lisle, Illinois 60532
               (Address of Principal Executive Offices) (Zip Code)

       REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (630) 241-4141

                        W. Scott Jardine, Esq., Secretary
                   First Trust Exchange-Traded AlphaDEX(TM) Fund
                            First Trust Advisors L.P.
                        1001 Warrenville Road, Suite 300
                              Lisle, Illinois 60532
                     (Name and Address of Agent for Service)

                                    Copy to:

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

It is proposed that this filing will become effective (check appropriate box):

[ ] immediately upon filing pursuant to paragraph (b)
[ ] on (date) pursuant to paragraph (b)
[ ] 60 days after filing pursuant to paragraph (a)(1)
[ ] on (date) pursuant to paragraph (a)(1)
[ ] 75 days after filing pursuant to paragraph (a)(2)
[ ] on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:



[ ] this post-effective amendment designates a new effective date for a
previously filed post-effective amendment.

This registration hereby amends Registrant's registration statement filed on
February 26, 2007 (the "Registration Statement") on such date or dates as may be
necessary to delay its effectiveness date until the Registrant shall file a
further amendment which specifically states that the Registration Statement
shall thereafter become effective in accordance with Section 8(a) of the
Securities Act of 1933 or until the Registration Statement shall become
effective on such date as the Securities and Exchange Commission, acting
pursuant to Section 8(a) may determine. Parts A, B and C of Registrant's
Registration Statement are incorporated by reference herein.






                                   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 on Form N-1A to be signed on its behalf by the undersigned, thereunto
duly authorized in the City of Lisle, in the State of Illinois, on the 7th day
of March, 2007.

                                  FIRST TRUST EXCHANGE-TRADED ALPHADEX(TM) FUND

                                  By: /s/ James A. Bowen
                                      ----------------------------------------
                                      James A. Bowen, President

         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                                                     DATE

/s/ Mark R. Bradley       Treasurer, Controller and Chief
- --------------------      Financial and Accounting Officer    March 7, 2007
Mark R. Bradley


/s/ James A. Bowen        President, Chief Executive
- ---------------------     Officer, Chairman and Trustee       March 7, 2007
James A. Bowen


*/s/ Richard E. Erickson  Trustee        )
- ------------------------                 )
Richard E. Erickson                      )
                                         )
*/s/ Thomas R. Kadlec     Trustee        )
- ------------------------                 )       By:   /s/ James A. Bowen
Thomas R. Kadlec                         )             ---------------------
                                         )             James A. Bowen
*/s/ Robert F. Keith      Trustee        )             Attorney-In-Fact
- ------------------------                 )             March 7, 2007
Robert F. Keith
                                         )
*/s/ Niel B. Nielson      Trustee        )
- ------------------------                 )
Niel B. Nielson                          )
                                         )

*    Original powers of attorney authorizing James A. Bowen, W. Scott Jardine
     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 and are incorporated by reference herein.