Masimo Corporation
US ˙ NasdaqGS ˙ US5747951003

SecurityMASI / Masimo Corporation
InstitutionMorgan Stanley
Latest Disclosed Ownership752,417 shares
Latest Disclosed Value $ 133,832,703
Morgan Stanley reports 18.28% decrease in ownership of MASI / Masimo Corporation

On May 15, 2026 - Morgan Stanley filed a 13F-HR form disclosing ownership of 752,417 shares of Masimo Corporation (US:MASI) valued at $133,832,412 USD as of March 31, 2026. The entity filed a previous 13F-HR/A on May 27, 2026 disclosing 920,735 shares of Masimo Corporation. This represents a change in shares of -18.28% during the quarter. The current value of the position is $134,547,208 USD.

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.

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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)
2026-05-15 2026-03-31 13F MASIMO COM 574795100 752,417 -168,318 -18.28 133,833 11.76 0.0081
2026-05-27 2025-12-31 13F/A-1 MASIMO COM 574795100 920,735 230,134 33.32 119,751 17.52 0.0071
2026-02-13 2025-12-31 13F MASIMO COM 574795100 920,735 230,134 119,751 0.0071
2026-05-27 2025-09-30 13F/A-1 MASIMO COM 574795100 690,601 -76,774 -10.00 101,899 -21.06 0.0062
2025-11-14 2025-09-30 13F MASIMO COM 574795100 690,601 -76,774 101,899 0.0062
2025-08-15 2025-06-30 13F MASIMO COM 574795100 767,375 31,593 4.29 129,088 5.31 0.0084
2025-05-15 2025-03-31 13F MASIMO COM 574795100 735,782 -2,059 -0.28 122,582 0.51 0.0088
2025-05-15 2024-12-31 13F/A-1 MASIMO COM 574795100 737,841 985 0.13 121,965 24.14 0.0085
2025-02-14 2024-12-31 13F MASIMO COM 574795100 737,841 985 121,965 0.0085
2025-05-14 2024-09-30 13F/A-2 MASIMO COM 574795100 736,856 261,053 54.87 98,245 63.95 0.0071
2025-02-14 2024-09-30 13F/A-1 MASIMO COM 574795100 736,856 261,053 98,245 0.0071
2024-11-14 2024-09-30 13F MASIMO COM 574795100 736,856 261,053 98,245 0.0071
2025-05-14 2024-06-30 13F/A-2 MASIMO COM 574795100 475,803 4,344 0.92 59,923 -13.45 0.0046
2024-10-17 2024-06-30 13F/A-1 MASIMO COM 574795100 475,803 4,344 59,923 0.0046
2024-08-14 2024-06-30 13F MASIMO COM 574795100 475,803 4,344 59,923 0.0046
2024-10-17 2024-03-31 13F/A-2 MASIMO COM 574795100 471,459 13,435 2.93 69,234 28.96 0.0056
2024-08-16 2024-03-31 13F/A-1 MASIMO COM 574795100 471,459 13,435 69,234 0.0007
2024-05-15 2024-03-31 13F MASIMO COM 574795100 471,459 13,435 69,234 0.0056
2024-08-16 2023-12-31 13F/A-1 MASIMO COM 574795100 458,024 -43,880 -8.74 53,685 21.99 0.0047
2024-02-13 2023-12-31 13F MASIMO COM 574795100 458,024 -43,880 53,685 0.0047
2023-11-15 2023-09-30 13F MASIMO COM 574795100 501,904 231,202 85.41 44,007 -1.21 0.0045
2023-08-14 2023-06-30 13F MASIMO COM 574795100 270,702 -40,558 -13.03 44,544 -22.45 0.0044
2023-05-15 2023-03-31 13F MASIMO COM 574795100 311,260 -171,995 -35.59 57,440 -19.66 0.0062
2023-02-14 2022-12-31 13F MASIMO COM 574795100 483,255 -212,587 -30.55 71,498 -27.21 0.0081
2022-11-14 2022-09-30 13F MASIMO COM 574795100 695,842 -680,782 -49.45 98,226 -45.40 0.0134
2022-10-27 2022-06-30 13F/A-1 MASIMO COM 574795100 1,376,624 886,202 180.70 179,885 152.03 0.0233
2022-08-15 2022-06-30 13F MASIMO COM 574795100 1,376,624 886,202 179,885 0.0047
2022-10-27 2022-03-31 13F/A-1 MASIMO COM 574795100 490,422 327,753 201.48 71,375 49.87 0.0096
2022-05-13 2022-03-31 13F MASIMO COM 574795100 490,422 327,753 71,375 0.0096
2022-02-14 2021-12-31 13F MASIMO COM 574795100 162,669 3,183 2.00 47,626 10.31 0.0059
2021-11-15 2021-09-30 13F MASIMO COM 574795100 159,486 71,836 81.96 43,175 103.17 0.0058
2021-08-23 2021-06-30 13F/A-1 MASIMO COM 574795100 87,650 -45,409 -34.13 21,251 -30.46 0.0028
2021-08-16 2021-06-30 13F MASIMO COM 574795100 87,650 -45,409 21,251 0.0006
2021-05-17 2021-03-31 13F MASIMO COM 574795100 133,059 -59,153 -30.77 30,559 -40.76 0.0045
2021-02-16 2020-12-31 13F MASIMO COM 574795100 192,212 133,769 228.89 51,587 273.95 0.0080
2020-11-13 2020-09-30 13F MASIMO COM 574795100 58,443 -19,776 -25.28 13,795 -22.64 0.0027
2020-08-14 2020-06-30 13F MASIMO COM 574795100 78,219 9,599 13.99 17,833 46.73 0.0039
2020-05-26 2020-03-31 13F/A-1 MASIMO COM 574795100 68,620 -8,122 -10.58 12,154 0.21 0.0033
2020-05-15 2020-03-31 13F MASIMO COM 574795100 68,620 -8,122 12,154 933.6806
2020-02-14 2019-12-31 13F MASIMO COM 574795100 76,742 5,290 7.40 12,129 14.08 0.0028
2019-11-14 2019-09-30 13F MASIMO COM 574795100 71,452 4,491 6.71 10,632 6.68 0.0028
2019-08-14 2019-06-30 13F MASIMO COM 574795100 66,961 -180,590 -72.95 9,966 -70.89 0.0027
2019-05-15 2019-03-31 13F MASIMO COM 574795100 247,551 123,210 99.09 34,231 156.41 0.0097
2019-02-14 2018-12-31 13F MASIMO COM 574795100 124,341 -61,917 -33.24 13,350 -42.45 0.0040
2019-04-23 2018-09-30 13F/A-2 MASIMO COM 574795100 186,258 -171,839 -47.99 23,196 -33.67 0.0058
2018-11-20 2018-09-30 13F/A-1 MASIMO COM 574795100 186,258 0 23,196 0.0058
2018-11-14 2018-09-30 13F MASIMO COM 574795100 186,258 -171,839 23,196
2019-04-23 2018-06-30 13F/A-1 MASIMO COM 574795100 358,097 -222,361 -38.31 34,968 -31.50 0.0094
2018-08-14 2018-06-30 13F MASIMO COM 574795100 358,097 -222,361 34,968
2019-04-23 2018-03-31 13F/A-1 MASIMO COM 574795100 580,458 79,008 15.76 51,050 20.05 0.0142
2018-05-14 2018-03-31 13F MASIMO COM 574795100 580,458 79,008 51,050
2019-04-23 2017-12-31 13F/A-1 MASIMO COM 574795100 501,450 116,653 30.32 42,523 27.67 0.0116
2018-02-14 2017-12-31 13F MASIMO COM 574795100 501,450 116,653 42,523
2017-11-14 2017-09-30 13F MASIMO COM 574795100 384,797 202,936 111.59 33,308 100.88 0.0100
2017-08-11 2017-06-30 13F MASIMO COM 574795100 181,861 -110,135 -37.72 16,581 -39.11 0.0050
2017-05-22 2017-03-31 13F/A-1 MASIMO COM 574795100 291,996 83,564 40.09 27,232 93.85 0.0084
2017-05-12 2017-03-31 13F MASIMO COM 574795100 291,996 27,232
2017-02-22 2016-12-31 13F/A-1 MASIMO COM 574795100 208,432 -94,787 -31.26 14,048 -22.12 0.0046
2017-02-13 2016-12-31 13F MASIMO COM 574795100 208,432 14,048
2016-11-10 2016-09-30 13F MASIMO COM 574795100 303,219 16,999 5.94 18,039 20.02 0.0062
2016-08-12 2016-06-30 13F MASIMO COM 574795100 286,220 -159,553 -35.79 15,030 -19.41 0.0054
2016-05-12 2016-03-31 13F MASIMO COM 574795100 445,773 -74,633 -14.34 18,651 -13.66 0.0072
2016-02-09 2015-12-31 13F MASIMO COM 574795100 520,406 15,718 3.11 21,601 11.00 0.0078
2016-02-08 2015-09-30 13F/A-1 MASIMO COM 574795100 504,688 104,538 26.12 19,461 25.54 0.0072
2015-11-09 2015-09-30 13F MASIMO COM 574795100 504,688 19,461
2015-08-12 2015-06-30 13F MASIMO COM 574795100 400,150 75,755 23.35 15,502 44.89 0.0054
2015-05-14 2015-03-31 13F MASIMO COM 574795100 324,395 -18,249 -5.33 10,699 18.55 0.0039
2015-02-13 2014-12-31 13F MASIMO COM 574795100 342,644 101,362 42.01 9,025 75.75 0.0033
2014-12-16 2014-09-30 13F/A-1 MASIMO COM 574795100 241,282 155,313 180.66 5,135 118.79 0.0020
2014-11-14 2014-09-30 13F MASIMO COM 574795100 241,282 5,135
2014-05-13 2014-03-31 13F MASIMO COM 574795100 85,969 -4,428 -4.90 2,347 -11.17 0.0010
2014-02-13 2013-12-31 13F MASIMO COM 574795100 90,397 12,187 15.58 2,642 26.78 0.0011
2013-11-13 2013-09-30 13F MASIMO CORP COM ST COM 574795100 78,210 -42,884 -35.41 2,084 -18.78 0.0010
2013-08-08 2013-06-30 13F MASIMO CORP COM ST COM 574795100 121,094 121,094 2,566 0.0013
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.