MASIMO CORP (MASI) Stock Institutional Trading Activity


MASIMO CORP (MASI) position changes reported by tracked institutional filers across multiple SEC 13F reporting periods. Based on recent SEC 13F filings (Q4 2025), investors with some of the largest reported share count changes include Viking Global Investors, Renaissance Technologies LLC, Durable Capital Partners, Fundsmith, and Polen Capital Management. Explore insights into buying and selling patterns, position changes, and investment conviction levels to understand institutional trading behavior and market dynamics.

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Portfolio quarterNameTypeQuantityRemainingReported stock balance
Q1 2020FundsmithSell-99,110475,853$84,283
Q1 2020Polen Capital ManagementBuy2,89110,534$1,866
Q1 2020Renaissance Technologies LLCSell-7,02119,000$3,365
Q4 2019Polen Capital ManagementBuy1,0357,643$1,208
Q4 2019Renaissance Technologies LLCSell-78,67926,021$4,113
Q3 2019Polen Capital ManagementBuy1026,608$983
Q3 2019Renaissance Technologies LLCSell-169,300104,700$15,578
Q2 2019FundsmithBuy84,300574,963$85,566
Q2 2019Polen Capital ManagementBuy4326,506$968
Q2 2019Renaissance Technologies LLCSell-71,000274,000$40,777
Q1 2019FundsmithBuy11,291490,663$67,849
Q1 2019Polen Capital ManagementBuy3516,074$840
Q1 2019Renaissance Technologies LLCSell-193,300345,000$47,707
Q4 2018FundsmithBuy479,372479,372$51,470
Q4 2018Polen Capital ManagementBuy1,8495,723$614
Q4 2018Renaissance Technologies LLCBuy235,500538,300$57,797
Q3 2018Polen Capital ManagementBuy3223,874$482
Q3 2018Renaissance Technologies LLCSell-208,700302,800$37,711
Q2 2018Polen Capital ManagementBuy3843,552$347
Q1 2018Polen Capital ManagementBuy3,1683,168$279
Q1 2018Renaissance Technologies LLCSell-40,600511,500$44,986
Q4 2017Renaissance Technologies LLCSell-131,300552,100$46,818
Q3 2017Renaissance Technologies LLCBuy62,900683,400$59,155
Q2 2017Renaissance Technologies LLCBuy191,400620,500$56,577
Q1 2017Renaissance Technologies LLCBuy255,700429,100$40,018
Q4 2016Renaissance Technologies LLCBuy94,900173,400$11,687
Q3 2016Renaissance Technologies LLCSell-65,30078,500$4,670
Q2 2016Renaissance Technologies LLCSell-88,900143,800$7,552
Q1 2016Renaissance Technologies LLCBuy10,300232,700$9,736
Q1 2016Jensen Investment ManagementBuy10,26010,260$429

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.