Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionDimensional Fund Advisors Lp
Latest Disclosed Ownership15,456,039 shares
Latest Disclosed Value $ 1,858,937,753
Dimensional Fund Advisors Lp reports 23.79% increase in ownership of MRK / Merck & Co., Inc.

On May 7, 2026 - Dimensional Fund Advisors Lp filed a 13F-HR form disclosing ownership of 15,456,039 shares of Merck & Co., Inc. (MX:MRK) valued at $1,858,937,753 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 12,486,183 shares of Merck & Co., Inc.. This represents a change in shares of 23.79% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

Upgrade to unlock premium data and export to Excel .

Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-07 2026-03-31 13F MERCK COM 58933Y105 15,456,039 2,969,856 23.79 1,858,938 41.43 0.0832
2026-02-12 2025-12-31 13F MERCK COM 58933Y105 12,486,183 1,608,609 14.79 1,314,396 44.04 0.2757
2025-11-12 2025-09-30 13F MERCK COM 58933Y105 10,877,574 254,432 2.40 912,509 8.51 0.1958
2025-08-12 2025-06-30 13F MERCK COM 58933Y105 10,623,142 -291,085 -2.67 840,950 -14.15 0.1947
2025-05-13 2025-03-31 13F MERCK COM 58933Y105 10,914,227 -663,308 -5.73 979,604 -14.94 0.2435
2025-02-13 2024-12-31 13F MERCK COM 58933Y105 11,577,535 4,480,007 63.12 1,151,642 42.88 0.2766
2024-11-07 2024-09-30 13F MERCK COM 58933Y105 7,097,528 895,602 14.44 806,002 4.95 0.1955
2024-08-09 2024-06-30 13F MERCK COM 58933Y105 6,201,926 431,074 7.47 767,965 0.85 0.2006
2024-05-10 2024-03-31 13F MERCK COM 58933Y105 5,770,852 -168,673 -2.84 761,464 17.60 0.2062
2024-02-07 2023-12-31 13F MERCK COM 58933Y105 5,939,525 -2,807,658 -32.10 647,521 -28.10 0.1891
2023-11-09 2023-09-30 13F MERCK COM 58933Y105 8,747,183 -886,535 -9.20 900,590 -18.98 0.2954
2023-08-09 2023-06-30 13F MERCK COM 58933Y105 9,633,718 130,427 1.37 1,111,549 9.94 0.3543
2023-05-12 2023-03-31 13F MERCK COM 58933Y105 9,503,291 240,981 2.60 1,011,034 98,345.37 0.3406
2023-02-09 2022-12-31 13F MERCK COM 58933Y105 9,262,310 476,216 5.42 1,028 -99.86 0.3036
2022-11-10 2022-09-30 13F MERCK COM 58933Y105 8,786,094 1,004,787 12.91 756,691 6.66 0.2905
2022-08-12 2022-06-30 13F MERCK COM 58933Y105 7,781,307 248,172 3.29 709,459 14.78 0.2545
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 7,533,135 -1,532,304 -16.90 618,109 -11.04 0.1904
2022-02-09 2021-12-31 13F MERCK COM 58933Y105 9,065,439 -726,533 -7.42 694,794 -5.53 0.2101
2021-11-12 2021-09-30 13F MERCK COM 58933Y105 9,791,972 -121,796 -1.23 735,481 -4.60 0.2369
2021-08-12 2021-06-30 13F MERCK COM 58933Y105 9,913,768 -232,786 -2.29 770,967 -1.44 0.2441
2021-05-14 2021-03-31 13F MERCK & CO. COM 58933Y105 10,146,554 -37,537 -0.37 782,194 -6.10 0.2587
2021-03-08 2020-12-31 13F/A-2 MERCK & CO. COM 58933Y105 10,184,091 -156,598 -1.51 832,995 -2.88 0.3008
2021-02-11 2020-12-31 13F MERCK & CO. COM 58933Y105 10,184,091 -156,598 832,995 300,833.5179
2020-11-12 2020-09-30 13F MERCK & CO. COM 58933Y105 10,340,689 377,526 3.79 857,680 11.33 0.3637
2020-08-13 2020-06-30 13F MERCK & CO. COM 58933Y105 9,963,163 430,326 4.51 770,370 5.03 0.3386
2020-05-14 2020-03-31 13F MERCK & CO. COM 58933Y105 9,532,837 529,406 5.88 733,455 -10.43 0.3821
2020-02-14 2019-12-31 13F MERCK COM 58933Y105 9,003,431 257,378 2.94 818,870 11.23 0.2984
2019-11-12 2019-09-30 13F MERCK COM 58933Y105 8,746,053 973,889 12.53 736,183 12.96 0.2861
2019-08-13 2019-06-30 13F MERCK COM 58933Y105 7,772,164 682,967 9.63 651,703 10.53 0.2530
2019-08-12 2019-03-31 13F/A-2 MERCK COM 58933Y105 7,089,197 369,456 5.50 589,596 14.83 0.2348
2019-05-10 2019-03-31 13F MERCK COM 58933Y105 7,089,197 369,456 589,596
2019-02-26 2018-12-31 13F/A-1 MERCK COM 58933Y105 6,719,741 -34,285 -0.51 513,430 7.16 0.2326
2019-02-13 2018-12-31 13F MERCK COM 58933Y105 6,719,741 -34,285 513,430
2018-11-13 2018-09-30 13F MERCK COM 58933Y105 6,754,026 12,807 0.19 479,118 17.09 0.1824
2018-08-10 2018-06-30 13F MERCK COM 58933Y105 6,741,219 8,426 0.13 409,181 11.57 0.1631
2018-05-11 2018-03-31 13F MERCK COM 58933Y105 6,732,793 13,132 0.20 366,735 -3.01 0.1528
2018-02-12 2017-12-31 13F MERCK COM 58933Y105 6,719,661 39,009 0.58 378,130 -11.60 0.1567
2017-11-13 2017-09-30 13F MERCK COM 58933Y105 6,680,652 -6,172 -0.09 427,772 -0.19 0.1869
2017-08-11 2017-06-30 13F MERCK COM 58933Y105 6,686,824 -76,930 -1.14 428,574 -0.28 0.1979
2017-05-12 2017-03-31 13F MERCK COM 58933Y105 6,763,754 128,351 1.93 429,761 10.01 0.2054
2017-02-09 2016-12-31 13F MERCK COM 58933Y105 6,635,403 48,710 0.74 390,642 -4.96 0.1951
2016-11-10 2016-09-30 13F MERCK COM 58933Y105 6,586,693 262,937 4.16 411,049 12.84 0.2222
2016-08-09 2016-06-30 13F MERCK COM 58933Y105 6,323,756 188,743 3.08 364,285 12.22 0.2096
2016-05-13 2016-03-31 13F MERCK & CO INC COM 58933Y105 6,135,013 209,360 3.53 324,615 3.71 0.1943
2016-02-10 2015-12-31 13F MERCK & CO INC COM 58933Y105 5,925,653 330,152 5.90 313,010 13.26 0.1951
2015-11-13 2015-09-30 13F MERCK & CO INC COM 58933Y105 5,595,501 613,779 12.32 276,352 -2.57 0.1814
2015-08-14 2015-06-30 13F MERCK & CO INC COM 58933Y105 4,981,722 -297,119 -5.63 283,639 -6.53 0.1737
2015-05-14 2015-03-31 13F MERCK & CO INC COM 58933Y105 5,278,841 42,890 0.82 303,448 2.04 0.1916
2015-02-06 2014-12-31 13F MERCK & CO INC COM 58933Y105 5,235,951 304,710 6.18 297,389 1.73 0.1953
2014-11-13 2014-09-30 13F MERCK & CO INC COM 58933Y105 4,931,241 27,806 0.57 292,336 3.07 0.2071
2014-08-08 2014-06-30 13F MERCK & CO INC COM 58933Y105 4,903,435 64,620 1.34 283,640 3.27 0.1972
2014-05-14 2014-03-31 13F MERCK & CO INC COM 58933Y105 4,838,815 -28,849 -0.59 274,650 12.74 0.2052
2014-02-12 2013-12-31 13F MERCK & CO INC COM 58933Y105 4,867,664 -51,518 -1.05 243,621 4.02 0.1898
2013-11-13 2013-09-30 13F MERCK & CO INC COM 58933Y105 4,919,182 -27,542 -0.56 234,196 1.90 0.2027
2013-08-15 2013-06-30 13F MERCK & CO INC COM 58933Y105 4,946,724 4,946,724 229,824 0.2164
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.