As filed with the Securities and Exchange Commission on September 23, 2013

Securities Act of 1933 File No. 333-173967

Investment Company Act of 1940 File No. 811-22555

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933                 x

Pre-Effective Amendment No.           ¨

Post-Effective Amendment No. 37 x

and/or

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940    x

Amendment No. 39   x

(Check Appropriate Box or Boxes)

FLEXSHARES TRUST

(Exact Name of Registrant as Specified in Charter)

50 South LaSalle Street

Chicago, Illinois 60603

(Address of Principal Executive Offices)

800-595-9111

(Registrant’s Telephone Number, including Area Code)

Name and Address of Agent for Service:	with a copy to:
Diana E. McCarthy, Esq.	Peter K. Ewing
Drinker Biddle & Reath LLP	Craig R. Carberry, Esq.
One Logan Square, Ste. 2000	Northern Trust Investments, Inc.
Philadelphia, Pennsylvania 19103-6996	50 South LaSalle 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 October 7, 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.

Explanatory Note

This Post-Effective Amendment No. 37 to the Registrant’s Registration Statement on Form N-1A is being filed pursuant to Rule 485(b)(1)(iii) of the Securities Act of 1933, as amended (“1933 Act”), solely for the purpose of delaying until October 7, 2013 the effectiveness of the Registrant’s Post-Effective Amendment No. 34 filed on July 5, 2013, which, pursuant to Rule 485(a)(2) of the 1933 Act, was scheduled to become effective on September 18, 2013. Post-Effective Amendment No. 35 was filed on September 9, 2013 pursuant to Rule 485(b)(1)(iii) to extend the effective date of Post-Effective Amendment No. 34 to September 25, 2013. This Post-Effective Amendment No. 37 incorporates by reference the information contained in Parts A , B and C of Post-Effective Amendment No. 34 to the Registrant’s Registration Statement, filed on July 5, 2013.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended (the “Securities Act”), and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all the requirements for the effectiveness of this Post-Effective Amendment No. 37 pursuant to Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment No. 37 to its Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Chicago and State of Illinois on the 23rd day of September 2013.

FLEXSHARES TRUST

By: /s/ Shundrawn A. Thomas

Shundrawn A. Thomas

Trustee and President

Pursuant to the requirements of the Securities Act, this Post-Effective Amendment No. 37 to Registrant’s Registration Statement has been signed below by the following persons in the capacities and on the date indicated.

Name	Title	Date
* Sarah N. Garvey	Trustee	September 23, 2013
Sarah N. Garvey
* Philip G. Hubbard	Trustee	September 23, 2013
Philip G. Hubbard
* Eric T. McKissack	Trustee	September 23, 2013
Eric T. McKissack
/s/ Shundrawn A. Thomas	Trustee and President	September 23, 2013
Shundrawn A. Thomas	(Principal Executive Officer)
/s/ Randal Rein	Treasurer	September 23, 2013
Randal Rein	(Principal Financial Officer and Principal Accounting Officer)

* By: /s/ Diana E. McCarthy

Diana E. McCarthy

Attorney-In-Fact, pursuant to power of attorney