FlexShares® Trust Semiannual Report April 30, 2019 Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of FlexShares® Trust’s shareholder reports like this one will no longer be sent by mail, unless you specifically request paper copies of the reports from FlexShares® Trust or your financial intermediary, such as a broker-dealer or bank. Instead, the reports will be made available on FlexShares® Trust’s website (www.flexshares.com) and you will be notified by mail each time a report is posted and provided with a website link to access the report. If you have already elected to receive your shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from FlexShares® Trust electronically at any time by contacting your financial intermediary. You may elect to receive all future reports in paper free of charge. Please contact your financial intermediary to continue receiving paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds in FlexShares® Trust that you hold in your account at the financial intermediary. You must provide separate instructions to each of your financial intermediaries. Table of Contents Statements of Assets and Liabilities ................................................ 2 Statements of Operations................................................................. 9 Statements of Changes in Net Assets............................................. 16 Financial Highlights ........................................................................... 30 Schedules of Investments ................................................................. 56 FlexShares® Morningstar US Market Factor Tilt Index Fund ............ 56 FlexShares® Morningstar Developed Markets ex-US Factor Tilt Index Fund......................................................................................... 91 FlexShares® Morningstar Emerging Markets Factor Tilt Index Fund.................................................................................................... 136 FlexShares® Currency Hedged Morningstar DM ex-US Factor Tilt Index Fund......................................................................................... 177 FlexShares® Currency Hedged Morningstar EM Factor Tilt Index Fund.................................................................................................... 179 FlexShares® US Quality Large Cap Index Fund ................................ 181 FlexShares® STOXX® US ESG Impact Index Fund ............................ 185 FlexShares® STOXX® Global ESG Impact Index Fund ..................... 193 FlexShares® Morningstar Global Upstream Natural Resources Index Fund......................................................................................... 207 FlexShares® STOXX® Global Broad Infrastructure Index Fund........ 215 FlexShares® Global Quality Real Estate Index Fund......................... 221 FlexShares® Real Assets Allocation Index Fund................................. 225 FlexShares® Quality Dividend Index Fund ......................................... 226 FlexShares® Quality Dividend Defensive Index Fund........................ 232 FlexShares® Quality Dividend Dynamic Index Fund ......................... 237 FlexShares® International Quality Dividend Index Fund................... 242 FlexShares® International Quality Dividend Defensive Index Fund.................................................................................................... 249 FlexShares® International Quality Dividend Dynamic Index Fund... 256 FlexShares® iBoxx 3-Year Target Duration TIPS Index Fund ............ 262 FlexShares® iBoxx 5-Year Target Duration TIPS Index Fund ............ 263 FlexShares® Disciplined Duration MBS Index Fund .......................... 264 FlexShares® Credit-Scored US Corporate Bond Index Fund............ 268 FlexShares® Credit-Scored US Long Corporate Bond Index Fund.................................................................................................... 277 FlexShares® High Yield Value-Scored Bond Index Fund .................. 284 FlexShares® Ready Access Variable Income Fund............................ 293 FlexShares® Core Select Bond Fund................................................... 303 Notes to the Financial Statements................................................... 305 Fund Expenses ................................................................................... 344 Supplemental Information ............................................................... 348 For More Information ....................................................................... 357 FlexShares® Trust Statements of Assets and Liabilities April 30, 2019 (Unaudited) FlexShares® FlexShares® Morningstar Morningstar FlexShares® FlexShares® Developed Emerging Currency Hedged Morningstar US Markets ex-US Markets Morningstar DM Market Factor Tilt Factor Tilt Factor Tilt ex-US Factor Tilt Index Fund Index Fund Index Fund Index Fund ASSETS Securities, at cost $ 983,596,928 $ 916,760,077 $510,572,404 $ — Affiliate securities, at cost 380,880 — — 8,738,297 Securities Lending Reinvestments, at cost 103,201,582 14,484,118 3,577,822 — Securities, at value† 1,478,882,201 1,013,811,165 577,172,319 — Affiliate securities, at value 625,792 — — 8,399,144 Securities Lending Reinvestments, at value 103,209,542 14,484,118 3,577,822 — Cash 22,183,488 3,542,734 3,597,851 965 Cash segregated at broker* 41,548 1,226,568 180,750 3 Foreign cash†† — 8,989,753 2,385,467 — Restricted cash** — — — — Due from Authorized Participant — — — — Unrealized appreciation on forward foreign currency contracts — 14,878 42,394 30,338 Receivables: ———— Dividends and interest 1,050,442 6,849,196 1,014,826 — Securities lending income 25,946 102,330 25,152 — Capital shares issued — — — — Investment adviser 81,597 59,150 30,781 957 Securities sold — 54,899 39,845 — Variation margin on futures contracts 1,148,100 773,845 203,613 — Total Assets 1,607,248,656 1,049,908,636 588,270,820 8,431,407 LIABILITIES Unrealized depreciation on forward foreign currency contracts — 46,323 11,551 11,373 Payables: Cash collateral received from securities loaned 103,184,691 14,484,118 3,577,822 — Deferred compensation (Note 7) 78,965 57,529 29,715 564 Investment advisory fees (Note 4) 304,948 330,635 286,919 186 Trustee fees (Note 7) 8,679 5,792 3,486 428 Securities purchased — 2 1 — Deferred non-US capital gains taxes — — — — Due to Authorized Participant — — — — Capital shares redeemed — — — — Other 15,000 100,000 100,000 — Total Liabilities 103,592,283 15,024,399 4,009,494 12,551 Net Assets $1,503,656,373 $1,034,884,237 $584,261,326 $ 8,418,856 NET ASSETS CONSIST OF: Paid-in capital $1,039,296,668 $1,018,101,478 $570,984,957 $ 9,658,033 Distributable earnings (loss) 464,359,705 16,782,759 13,276,369 (1,239,177) Net Assets $1,503,656,373 $1,034,884,237 $584,261,326 $ 8,418,856 Shares Outstanding (unlimited number of shares authorized $ 0.0001 par value) 12,700,001 16,600,001 10,900,001 300,001 Net Asset Value $ 118.40 $ 62.34 $ 53.60 $ 28.06 † Securities on loan, at value $ 141,912,223 $ 97,728,258 $ 23,130,022 $ — †† Cost of foreign cash $ — $ 9,025,765 $ 2,407,208 $ — * Includes cash pledged by the Fund to cover margin requirements for open futures contracts as of 04/30. ** Includes cash pledged by an Authorized Participant for missing deposit securities required to secure Creation Units. See Accompanying Notes to the Financial Statements. 2 FLEXSHARES SEMIANNUAL REPORT Statements of Assets and Liabilities (cont.) FlexShares® FlexShares® Currency Hedged FlexShares® FlexShares® STOXX® Morningstar EM US Quality STOXX® US Global ESG Factor Tilt Large Cap ESG Impact Impact Index Fund Index Fund Index Fund Index Fund ASSETS Securities, at cost $ — $75,110,140 $38,152,052 $65,504,070 Affiliate securities, at cost 5,851,436 — 32,116 31,320 Securities Lending Reinvestments, at cost — 653,504 111,491 879,269 Securities, at value† — 81,260,702 45,144,270 73,125,506 Affiliate securities, at value 5,789,714 — 33,310 32,521 Securities Lending Reinvestments, at value — 653,504 111,491 879,269 Cash 37,020 1,173,208 272,036 252,942 Cash segregated at broker* 14,847 73,312 37,461 42,132 Foreign cash†† — — — 362,658 Restricted cash** — ——— Due from Authorized Participant — — — — Unrealized appreciation on forward foreign currency contracts 42,495 — — — Receivables: — ——— Dividends and interest — 49,062 51,748 218,299 Securities lending income — 535 313 979 Capital shares issued — — — — Investment adviser 1,722 1,910 1,079 2,008 Securities sold — ——— Variation margin on futures contracts 2,132 64,178 13,684 31,924 Total Assets 5,887,930 83,276,411 45,665,392 74,948,238 LIABILITIES Unrealized depreciation on forward foreign currency contracts 921 — — — Payables: Cash collateral received from securities loaned — 653,504 111,491 879,269 Deferred compensation (Note 7) 1,404 1,518 726 1,529 Investment advisory fees (Note 4) 88 21,599 11,417 25,212 Trustee fees (Note 7) 345 734 530 768 Securities purchased — — 3,146 — Deferred non-US capital gains taxes — — — — Due to Authorized Participant — — — — Capital shares redeemed — — — — Other — 3,500 1,400 7,500 Total Liabilities 2,758 680,855 128,710 914,278 Net Assets $ 5,885,172 $82,595,556 $45,536,682 $74,033,960 NET ASSETS CONSIST OF: Paid-in capital $ 7,720,944 $77,734,603 $39,569,940 $68,228,604 Distributable