1933 Act Registration No. 333-171759
                                             1940 Act Registration No. 811-22519

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933                     [ ]
Pre-Effective Amendment No. __                                              [ ]
Post-Effective Amendment No. 35                                             [X]
                                     and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940             [ ]
Amendment No. 36                                                            [X]

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

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

REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (800) 621-1675

W. Scott Jardine, Esq., Secretary
First Trust Exchange-Traded AlphaDEX Fund II
First Trust Advisors L.P.
120 East Liberty Drive, Suite 400
Wheaton, Illinois 60187
(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)
[X] on May 3, 2013 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:

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

CONTENTS OF POST-EFFECTIVE AMENDMENT NO. 35

This Post-Effective Amendment to the Registration Statement comprises the following papers and contents:

The Facing Sheet

The sole purpose of this filing is to delay the effectiveness of the Registrant's Post-Effective Amendment No. 9, as it relates to First Trust Global Agriculture AlphaDEX(R) Fund, a series of the Registrant, until May 3, 2013. Parts A, B and C of the Registrant's Post-Effective Amendment No. 9 under the Securities Act of 1933 as it relates to First Trust Global Agriculture AlphaDEX(R) Fund, filed on April 20, 2012, are incorporated by reference herein.

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

SIGNATURE                             TITLE                  DATE
                                      President and Chief    April 4, 2013
/s/ Mark R. Bradley                   Executive Officer
-----------------------------------
    Mark R. Bradley
                                      Treasurer, Chief
                                      Financial Officer      April 4, 2013
                                      and Chief Accounting
/s/ James M. Dykas                    Officer
-----------------------------------
    James M. Dykas

                                                )
James A. Bowen*                         Trustee )
                                                )
                                                )
Richard E. Erickson*                    Trustee )
                                                )
                                                )
Thomas R. Kadlec*                       Trustee )      BY:  /s/ W. Scott Jardine
                                                )           --------------------
                                                )           W. Scott Jardine
Robert F. Keith*                        Trustee )           Attorney-In-Fact
                                                )           April 4, 2013
                                                )
Niel B. Nielson*                        Trustee )
                                                )