As filed with the Securities and Exchange Commission on April 19, 2013 
                                           1933 Act Registration No. 333-174332
                                            1940 Act Registration No. 811-22559

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

                                   FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933                      [ ]
Post-Effective Amendment No. __                                              [ ]
Post-Effective Amendment No. 34                                              [X]
                                     and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940              [ ]
Amendment No. 36                                                             [X]

FIRST TRUST EXCHANGE-TRADED FUND IV
(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 Fund IV
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):

[X] immediately upon filing pursuant to paragraph (b)
[ ] on ___________ 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 Statement relates to First Trust Senior Loan Fund, a
series of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act of 1933 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, duly authorized in the City of Wheaton, and State of Illinois, on the 19th day of April, 2013.

FIRST TRUST EXCHANGE-TRADED FUND IV 

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
/s/ Mark R. Bradley       President and Chief Executive         April 19, 2013
-----------------------   Officer
    Mark R. Bradley


/s/ James M. Dykas        Treasurer, Chief Financial Officer    April 19, 2013
-----------------------   and Chief Accounting Officer
    James M. Dykas

                                           )
James A. Bowen*                    Trustee )
                                           )
                                           )
Richard E. Erickson*               Trustee )
                                           )
                                           )     BY: /s/ W. Scott Jardine
Thomas R. Kadlec*                  Trustee )         -----------------------
                                           )             W. Scott Jardine
                                           )             Attorney-In-Fact
Robert F. Keith*                   Trustee )             April 19, 2013
                                           )
                                           )
Niel B. Nielson*                   Trustee )
                                           )

* Original powers of attorney authorizing James A. Bowen, W. Scott Jardine, Mark R. Bradley, Eric F. Fess and Kristi A. Maher 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, filed as an exhibit and are incorporated by reference herein.

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