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FlexShares Trust

 Faegre, Drinker Biddle & Reath LLP

191 N. Wacker Drive, Suite 3700

Chicago, IL 60606-1698

 (312) 569-1000 (Phone)

 (312) 569-3000 (Facsimile)

www.faegredrinker.com

February 21, 2020

 Via Edgar
Transmission

 Securities and Exchange Commission

100 F Street, N.E.

 Washington, D.C. 20549

Attention: Samantha Brutlag

RE:
 FlexShares® Trust (the “Trust” or
“Registrant”)

 Post-Effective Amendment No. 85 to Registration Statement on Form

N-1A (File Nos. 333-173967 and 811-22555)

 Dear Ms. Brutlag:

The following responds to comments that you provided to us by telephone on February 6, 2020, regarding the above-referenced
post-effective amendment to the Trust’s registration statement on Form N-1A (the “Post-Effective Amendment”), which was filed to reflect new underlying indexes for FlexShares® Credit-Scored US Long Corporate Bond Index Fund and FlexShares® Credit-Scored US Corporate Bond Index Fund (each, a “Fund,” and
together, the “Funds”).

 Our responses follow your comments. Terms not otherwise defined herein shall have the meaning ascribed
to them in the Registration Statement. The changes to the Trust’s disclosure discussed below will be reflected in a Post-Effective Amendment to the Trust’s Registration Statement (the “Amendment”) to be filed on or about
February 26, 2020.

 1.    Comment: Will the Funds’ names be changing, and if not, please explain supplementally to
the Staff why Fund names that refer to another index would not be confusing to investors. The Staff may have additional comments.

Response: The Funds’ names will not be changed. The Registrant does not believe that Fund names will be confusing to investors
because: (a) the transition from the old indexes to the new indexes will be clearly disclosed to shareholders in the Funds’ prospectus; and (b) NTI, as the index provider, has informed the Registrant that the old indexes will be
terminated upon transition to the new indexes on March 16, 2020. If that should change, NTI and the Funds will consider their options at that time to mitigate against possible shareholder confusion. Additionally, the Registrant believes that
the current Fund names are (a) consistent and descriptive of the Funds’ new underlying indexes and revised investment strategies; and (2) reasonably general that investors would not necessarily associate the Funds to their old
indexes.

 2.    Comment: Please explain supplementally to the Staff why the Funds are switching
indexes.

 Response: Since the old indexes were created in 2014 and 2015, NTI, as an index provider, developed the new indexes based
on research and market developments. NTI, as the Funds’ investment adviser, recommended the new indexes because it believes that the new index methodologies, with the removal of a liquidity screen and addition of a value factor, could enhance
the Funds’ respective risk/return profiles.

 3.    Comment: Comments with respect to one Fund apply to both Funds, as
applicable.

 Response: The Registrant so acknowledges.

4.    Comment: Please provide the Staff with the completed fee table and expense example for each Fund at least one-week prior to effectiveness.

 Response: Attached hereto as Appendix A are completed fee
tables and expense examples for each Fund, which will also be included in the Funds’ Prospectus.

 5.    Comment: Please
provide the staff with a white paper for each Fund’s Underlying Index.

 Response: Attached hereto as Appendix B are the index
methodologies for each Fund’s Underlying Index that were previously sent to you by email.

 6.    Comment: Please disclose
the number of index components in the Underlying Index for each Fund in the Principal Investment Strategies summary section. A range is acceptable.

Response: The Registrant agrees to disclose the number of index components in the applicable Underlying Index in each Fund’s
Principal Investment Strategies summary section of the Prospectus.

 7.    Comment: The Staff notes that each Fund’s
principal risks are listed in alphabetical order. Please prioritize the principal risks as to those most likely to adversely impact the Funds’ net asset values, yield and total return. After disclosing the most significant risks, the rest can
be alphabetized. See Improving Principal Risks Disclosure, ADI 2019-08.

Response: The Registrant has re-ordered the risk factors in response to this comment, but believes that the significance of each risk
factor may change over time and that the order of the risks is not intended to convey that one risk is more significant than another.

8.    Comment: In the Financial Sector Risk, please update the concentration information for 2019.

Response: The concentration information will be updated.

9.    Comment: Because there is a Non-US Issuer Risk included as a Principal Investment
Risk, please include corresponding disclosure in the Principal Investment Strategies summary section.

 Response: In response to
this comment, the Registrant will add the following disclosure to each Fund’s Principal Investment Strategies summary section:

“The Fund may invest in U.S. dollar denominated bonds of non-U.S. corporations to
the extent such bonds are included in the Underlying Index. Such investment will not exceed 20% of the net assets of the Fund.”

 2

 10.    Comment: Please provide the staff with updated performance information for each
Fund at least one-week prior to effectiveness. Also, please add footnote disclosure that the principal investment strategy has changed and the date it changed.

Response: Updated performance information with the requested footnote disclosure for each Fund is attached as Appendix C.

11.    Comment: The Principal Investment Strategy states that the “The Underlying Index begins with the Parent Index and then
follows a rules-based methodology to select and weight securities, subject to certain constraints, to optimize the Underlying Index’s exposure to a combined proprietary value score and a proprietary quality score, as determined by NTI acting in
its capacity as index provider (“Index Provider”).” Please explain what “subject to certain constraints” means.

Response: Further in that same paragraph, the disclosure states that: “[i]n addition, at the time of index reconstitution, the
weighting of the Underlying Index’s constituent securities are adjusted such that the effective duration and the sector exposures of the Underlying Index are similar to those of the Parent Index. Issuer and issue exposures are constrained to
manage concentration risk.” To clarify, the above disclosure will be revised as follows:

 “The Underlying Index
begins with the Parent Index and then follows a rules-based methodology to select and weight securities, subject to certain constraints as described below, to optimize the Underlying Index’s . . . .”

12.     Comment: Please make sure that the Investment Company Act file number appears in 8.0 modern type on the back cover of the
Prospectus.

 Response: The Registrant agrees to do so.

Sincerely,

/s/ Veena K. Jain

Veena K. Jain

Copy to:

Peter K. Ewing

Jeff Beeson

Jose Del Real

Diana E. McCarthy

 3

 APPENDIX A

FlexShares® Credit-Scored US Corporate Bond Index Fund

 Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Under the Fund’s Investment Advisory Agreement, the
Fund is responsible for the following expenses: interest expenses, brokerage commissions and other trading expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as
litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and customary brokerage commissions when buying or selling shares of the Fund in the secondary market, which are not reflected in the example
that follows:

Annual Fund Operating Expenses (expenses that you pay each
year as a percentage of the value of your investment)

 Management Fees

0.22
%

 Distribution (12b-1) Fees

0.00
%

 Other Expenses

0.01
%

 Total Annual Fund Operating Expenses

0.23
%

 Expense Reimbursement(1)

-0.01
%

 Total Annual Fund Operating Expenses After Expense Reimbursement

0.22
%

(1)
 Northern Trust Investments, Inc. (“NTI” or the “Adviser”) has contractually agreed to
reimburse a portion of the operating expenses of the Fund (other than Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.22%. This contractual limitation may not be terminated before March 1,
2021 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders.

 Example

 The following Example is
intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those
periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be
higher or lower, based on these assumptions your costs would be:

 1 Year

$
23

 3 Years

$
73

 5 Years

$
129

 10 Years

$
292

 A-1

 FlexShares®
Credit-Scored US Long Corporate Bond Index Fund

Fees and Expenses of the Fund

 This table describes the
fees and expenses that you may pay if you buy and hold shares of the Fund. Under the Fund’s Investment Advisory Agreement, the Fund is responsible for the following other expenses: interest expenses, brokerage commissions and other trading
expenses, fees and expenses of the independent trustees and their independent legal counsel, taxes and other extraordinary costs such as litigation and other expenses not incurred in the ordinary course of business. You will also incur usual and
customary brokerage commissions when buying or selling shares of the Fund in the secondary market, which are not reflected in the example that follows:

Annual Fund Operating Expenses (expenses that you pay each
year as a percentage of the value of your investment)

 Management Fees

0.22
%

 Distribution (12b-1) Fees

0.00
%

 Other Expenses

0.01
%

 Total Annual Fund Operating Expenses

0.23
%

 Expense Reimbursement(1)

-0.01
%

 Total Annual Fund Operating Expenses After Expense Reimbursement

0.22
%

(1)
 Northern Trust Investments, Inc. (“NTI” or the “Adviser”) has contractually agreed to
reimburse a portion of the operating expenses of the Fund (other than Acquired Fund Fees and Expenses) to the extent the “Total Annual Fund Operating Expenses” exceed 0.22%. This contractual limitation may not be terminated before March 1,
2021 without the approval of the Fund’s Board of Trustees. The Fund’s Board of Trustees may terminate the contractual agreement at any time if it determines that it is in the best interest of the Fund and its shareholders.

 Example

 The following Example is
intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those
periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same (taking into account the expense reimbursement arrangement for one year). Although your actual costs may be
higher or lower, based on these assumptions your costs would be:

 1 Year

$
 23

 3 Years

$
 73

 5 Years

$
129

 10 Years

$
292

 A-2

 APPENDIX B

 NORTHERN TRUST US CORPORATE BOND QUALITY VALUE INDEX

 Northern Trust

50 South La Salle Street

 Chicago, Illinois 60603

Nt_index_services@ntrs.com

 northerntrust.com

 INDEX METHODOLOGY

INTRODUCTION

 This document sets forth the methodology for
the Northern Trust US Corporate Bond Quality Value Index.

 The index is calculated and disseminated by Intercontinental Exchange Data Services (ICE).

OVERVIEW

 Northern Trust US Corporate Bond
Quality Value Index

 The Northern Trust US Corporate Bond Quality Value Index is designed to measure the performance of a diversified universe
of intermediate maturity, US-dollar denominated bonds of companies with investment grade credit quality, favorable valuations, and enhanced short-term and long-term solvency.

INDEX ELIGIBLITY

 In order to be eligible for inclusion
in the Northern Trust US Corporate Bond Quality Value Index, each bond issue must meet the following criteria at each reconstitution:

•

Currency: Each security must be issued in United States Dollars

•

Market of Issue: Each security must be publicly issued in the U.S. and SEC registered or eligible for resale under 144A of the Securities Act of 1933

•

Security Types: Each security must be one of the following types unless noted otherwise below:

•

Inclusions: Fixed rate debentures, Medium Term Notes (MTN), callable and putable bonds, original issue zero-coupon bonds, 144A securities with registration rights,
convertible, warrant-bearing and contingent capital securities, Fixed to floating capital securities (hybrids) which convert in a period of one year and up to (but not including) ten years from the reconstitution date, Payment in Kind (PIK) bonds, step-up coupons and those that change according to a predetermined schedule.

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Index Methodology: NT US Corporate Bond Quality Value Index
 1
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 B-1

 NORTHERN TRUST US CORPORATE BOND QUALITY VALUE INDEX

•

Exclusions: Illiquid securities with no external pricing per our calculation source ICE

•

Debt Seniority: Each security must be either senior or subordinated debt, but covered bonds are to be excluded.

•

Ratings: Each security must have a minimum credit rating of Baa3/BBB-/BBB-i

•

Maturity: Each security must have a final maturity of at least one year and up to (but not including) ten years, at the time of each reconstitution.

•

Size: Each security must have $250 million or more in outstanding principal at the time of each reconstitution.

DETAILED METHODOLOGY

 The construction of the index
begins with a securities screen to determine eligible securities (defined in “Index Eligibility” section). Once all eligible securities have been identified, the securities’ are then optimized based on their exposure to quantitative
factors such as:

•

Composite Alphaii: produced by combining each issue’s Value Scoreiii and Quality Scoreiv, as determined by Northern Trust Investments’ Quantitative Research Team

•

Effective Durationv

 The primary objective of the
optimization is to maximize our exposure to the Composite Alpha, and maintain a similar Effective Duration profile relative to our eligible universe. In addition to that main objective, systematic risk is managed during the optimization utilizing
several constraints. These constraints are listed below (bounds show as relative weightings unless otherwise noted):

•

Security level constraint: to limit an index constituent’s maximum or minimum weight versus the eligible universe to either full underweight or five times (5.0x) the weight in the eligible universe

•

Minimum absolute constituent constraint: to require that each index constituent has a weight of at least one basis point (0.01%)

•

Minimum absolute turnover constraint: to require that index turnover at the constituent level is larger than one basis point (0.01%) for each change made during the reconstitution

•

Sectorvi constraint: to limit the index’s maximum or minimum sector weight exposure to +/-10% versus the eligible
universe

•

Issuer level constraint: to limit each issuer’s absolute weight to 3.0% or less

 northerntrust.com  |
Index Metho