MASIMO CORP (MASI) Institutional Ownership Changes & 13F Activity

MASIMO CORP (MASI). Institutional ownership data tracks hedge funds, asset managers, and other institutional investors based on recent SEC Form 13F filings. This page analyzes institutional buying and selling activity, new holdings, and sold-out positions among tracked filers. Notable filers include Renaissance Technologies LLC, Viking Global Investors, First Eagle U.S. Value, Durable Capital Partners, and Fundsmith.

Portfolio quarterNameTypeQuantityRemainingReported stock balance
Q1 2026Renaissance Technologies LLCBuy179,600239,500$42,599,865
Q4 2025Viking Global InvestorsSell-559,093514,340$66,895,060
Q4 2025Renaissance Technologies LLCBuy34,52359,900$7,790,594
Q4 2025First Eagle U.S. ValueBuy2828$3,642
Q3 2025Durable Capital PartnersSell-543,279620,619$91,572,333
Q3 2025Viking Global InvestorsBuy306,0071,073,433$158,385,039
Q2 2025Viking Global InvestorsBuy767,426767,426$129,096,402
Q2 2025Durable Capital PartnersBuy38,2791,163,898$195,790,922
Q2 2025Renaissance Technologies LLCBuy10,37725,377$4,268,919
Q1 2025Durable Capital PartnersBuy1,125,6191,125,619$187,528,125
Q1 2025Renaissance Technologies LLCSell-26,23015,000$2,499,000
Q2 2023Renaissance Technologies LLCSell-40,07041,230$6,784
Q2 2023FundsmithSell-33,942730,377$120,183,535
Q1 2023Renaissance Technologies LLCSell-98,40081,300$15,003
Q4 2022Renaissance Technologies LLCBuy131,900179,700$26,587
Q4 2022FundsmithSell-842764,319$113,080,996
Q3 2022Renaissance Technologies LLCBuy41,60047,800$6,747
Q3 2022FundsmithBuy8,848765,161$108,010
Q2 2022FundsmithSell-4,783756,313$98,827
Q1 2022FundsmithBuy325,159761,096$110,770
Q4 2021Renaissance Technologies LLCBuy5,1006,200$1,815
Q4 2021FundsmithBuy927435,937$127,634
Q3 2021FundsmithBuy1,572435,010$117,762
Q2 2021FundsmithBuy2,375433,438$105,087
Q1 2021Renaissance Technologies LLCSell-81,5001,100$253
Q1 2021FundsmithBuy1,809431,063$98,998
Q4 2020FundsmithBuy357429,254$115,203
Q3 2020Renaissance Technologies LLCBuy67,70082,600$19,499
Q3 2020Polen Capital ManagementBuy2,72418,414$4,347
Q2 2020FundsmithSell-46,956428,897$97,784

Frequently asked questions about MASI activity

  • Which institutional owners are buying MASI?

    Institutional owners buying MASI include investors who have either initiated new positions or increased their existing holdings based on recent SEC 13F filings. The activity table above highlights which funds added shares in the latest reporting periods and how their positions changed over time.

  • What does "buy" mean in MASI activity?

    "Buy" means an investor increased their reported position in MASI compared to the prior reporting period. This reflects growing exposure to MASIMO CORP (MASI) rather than necessarily a brand-new position (though new positions also appear as buys when prior quantity was zero).

  • Is institutional interest in MASI increasing?

    Institutional interest in MASI can be assessed by comparing the number of tracked funds adding or increasing positions versus those trimming or exiting across the periods shown. A higher number of additions typically signals increasing participation among large filers, but it should be read alongside position sizes and the full table.

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