MASIMO CORP (MASI) Institutional Shareholders
MASIMO CORP (MASI) is currently reported in institutional portfolios tracked by InsiderSet based on the latest available SEC Form 13F filings for the quarter ended June 30, 2026. The institutional investors covered on this page collectively reported approximately $135.42M in MASI holdings during the latest filing period.
O'Connor Alternative Investments Llc is currently the largest disclosed institutional shareholder of MASI tracked by InsiderSet, reporting ownership valued at approximately $73.44M in its March 31, 2026 SEC Form 13F filing. Based on current market prices and the latest disclosed share count, the position is now estimated to be worth approximately $74.30M, representing an estimated gain of +1.17% since the filing period.
The top 10 institutional shareholders tracked on this page collectively account for approximately 100% of the total disclosed MASI value among the investors covered in this analysis. Major shareholders include O'Connor Alternative Investments Llc, Ubs Am, A Distinct Business Unit Of Ubs Asset Management Americas Llc, Cibra Capital Ltd, and several other long-term asset managers with concentrated positions in MASIMO CORP (MASI).
This page ranks the largest institutional MASI shareholders using publicly disclosed SEC Form 13F data, including reported values, estimated current holding values, portfolio allocation percentages, ownership concentration metrics, and historical holding changes across major hedge funds and investment firms.
Institutional Holders
14
Total Reported Value
$135.42M
Largest Holder
O'Connor Alternative Investments Llc
Largest Position
$73.44M
Insider Transactions (90d)
0
Latest Filing Quarter
Q2 2026
New Institutional Positions
108
Funds Exiting Positions
0
| Name | Investor/Manager | Portfolio % | Quantity | Reported Balance | Current Estimated Value | Gain/loss Since Filing | Estimated Portfolio Performance |
|---|---|---|---|---|---|---|---|
| O'Connor Alternative Investments Llc | 9.91% | 412,903 | $73,443,057 | $74,301,895 | +$858,838 | +1.17% | |
| Ubs Am, A Distinct Business Unit Of Ubs Asset Management Americas Llc | 0.00% | 133,689 | $23,779,262 | $24,057,336 | +$278,074 | +1.17% | |
| Cibra Capital Ltd | 7.76% | 90,376 | $16,075,179 | $16,263,161 | +$187,982 | +1.17% | |
| Cwm, Llc | 0.02% | 34,690 | $6,170,310 | $6,242,466 | +$72,156 | +1.17% | |
| Taconic Capital Advisors Lp | 86.47% | 30,000 | $5,336,100 | $5,398,500 | +$62,400 | +1.17% | |
| Advisors Asset Management, Inc. | 0.05% | 13,028 | $3,814,338 | $2,344,389 | -$1,469,949 | -38.54% | |
| Janus Henderson Group Plc | 0.00% | 20,000 | $3,557,000 | $3,599,000 | +$42,000 | +1.18% | |
| Pathstone Holdings, Llc | 0.01% | 7,386 | $1,313,747 | $1,329,111 | +$15,364 | +1.17% | |
| Op Asset Management Ltd | 0.01% | 6,308 | $930,745 | $1,135,125 | +$204,380 | +21.96% | |
| M&T Bank Corp | 0.00% | 3,516 | $625,830 | $632,704 | +$6,874 | +1.10% | |
| Brooklyn Investment Group | 0.01% | 2,015 | $358,409 | $362,599 | +$4,190 | +1.17% | |
| Ifp Advisors, Inc | 0.00% | 88 | $15,836 | $15,836 | -$0 | -0.00% | |
| Huntington National Bank | 0.00% | 2 | $360 | $360 | -$0 | -0.03% | |
| Bare Financial Services, Inc | 0.00% | 2 | $356 | $360 | +$4 | +1.10% |
Frequently asked questions about MASI
Who owns the most MASI stock?
The largest holders of MASI are typically major institutional investors such as asset managers and hedge funds reporting on Form 13F. The table above ranks tracked superinvestors by reported position size using the latest available filings for MASIMO CORP (MASI).
Is MASI widely held by superinvestors?
Many widely followed stocks like MASI appear across numerous superinvestor portfolios because of liquidity, index inclusion, and fundamentals. The holder count and table above show how broadly MASI is represented among the institutional managers we track.
What do “Current Estimated Value”, “Gain/loss Since Filing”, and “Estimated Portfolio Performance” mean?
Current Estimated Value is reported share quantity from the latest 13F times our most recent split-adjusted U.S. session close. Gain/loss Since Filing is that estimate minus the reported 13F dollar value; Estimated Portfolio Performance is that difference as a percent of the reported value. Green means the estimate is above the filing value; red means below (not purchase cost). If many filers share the same implied filing price per share, the performance % may match across rows. These are not official fund marks or live quotes.