Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in MASI held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 4.6M | $826.1M | -47.5% | 8.870% | 0.01% |
| 2 | Politan Capital Management LP | 4.6M | $816.4M | 0.0% | 8.765% | 82.89% |
| 3 | Pentwater Capital Management LP | 3.2M | $564.9M | β | 6.065% | 2.94% |
| 4 | BARCLAYS PLC | 2.7M | $488.1M | +4602.0% | 5.240% | 0.20% |
| 5 | HBK INVESTMENTS L P | 2.6M | $458.2M | β | 4.919% | 5.96% |
| 6 | MASSACHUSETTS FINANCIAL SERVICES CO /MA/ | 2.3M | $416.7M | -12.0% | 4.474% | 0.14% |
| 7 | VANGUARD CAPITAL MANAGEMENT LLC | 2.1M | $364.6M | β | 3.915% | 0.01% |
| 8 | VANGUARD PORTFOLIO MANAGEMENT LLC | 2.0M | $357.0M | β | 3.832% | 0.02% |
| 9 | FMR LLC | 1.5M | $258.1M | -81.5% | 2.771% | 0.01% |
| 10 | STATE STREET CORP | 1.4M | $255.7M | +1.6% | 2.745% | 0.01% |
| 11 | GOLDMAN SACHS GROUP INC | 984K | $175.1M | +54.6% | 1.879% | 0.02% |
| 12 | GEODE CAPITAL MANAGEMENT, LLC | 957K | $170.2M | +0.3% | 1.827% | 0.01% |
| 13 | AQR CAPITAL MANAGEMENT LLC | 832K | $147.4M | -23.8% | 1.589% | 0.07% |
| 14 | MORGAN STANLEY | 752K | $133.8M | -18.3% | 1.437% | 0.01% |
| 15 | CITIGROUP INC | 533K | $94.9M | +340.0% | 1.019% | 0.04% |
| 16 | FIL Ltd | 482K | $85.7M | β | 0.920% | 0.07% |
| 17 | Vivaldi Asset Management, LLC | 479K | $85.3M | β | 0.915% | 4.48% |
| 18 | HSBC HOLDINGS PLC | 473K | $84.3M | β | 0.904% | 0.04% |
| 19 | UBS Group AG | 468K | $83.3M | -21.9% | 0.894% | 0.01% |
| 20 | Liontrust Investment Partners LLP | 628K | $81.7M | 0.0% | 1.199% | 1.21% |
| 21 | Magnetar Financial LLC | 427K | $76.0M | +7729.2% | 0.816% | 0.77% |
| 22 | CNH PARTNERS LLC | 417K | $73.9M | β | 0.796% | 1.21% |
| 23 | Neuberger Berman Group LLC | 403K | $71.7M | +7956.5% | 0.770% | 0.05% |
| 24 | Walleye Trading LLC | 392K | $69.6M | β | 0.748% | 0.18% |
| 25 | NORTHERN TRUST CORP | 390K | $69.4M | +2.6% | 0.746% | 0.01% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). β% of Fundβ shows how much of that investorβs total 13F portfolio is invested in MASI β a direct measure of their conviction.
Filings activity in MASI during Q1 2026, grouped by how each filer changed its position.
Institutions that opened a new MASI position in Q1 2026
Institutions that fully closed their MASI position in Q1 2026
8 quarters of 13F filings Β· Ξ columns show change vs prior quarter
| Quarter | Inst. Holders | Ξ Holders | Ownership % | Ξ Ownership | Total 13F Value | Ξ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 432 | +12% | 94.83% | +22.87 pp | $8.94B | +32% |
| Q4 2025 | 385 | +13% | 71.96% | 11.22 pp | $6.78B | 13% |
| Q3 2025 | 342 | 8.1% | 83.18% | 13.34 pp | $7.84B | 14% |
| Q2 2025 | 372 | 3.9% | 96.52% | +5.20 pp | $9.10B | +5.7% |
| Q1 2025 | 387 | +7.5% | 91.32% | +1.50 pp | $8.61B | +1.7% |
| Q4 2024 | 360 | +3.2% | 89.82% | +22.12 pp | $8.46B | +33% |
| Q3 2024 | 349 | +0.9% | 67.70% | +5.66 pp | $6.38B | +9.1% |
| Q2 2024 | 346 | β | 62.04% | β | $5.85B | β |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Ξ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying MASI stock.
Based on Q1 2026 13F filings, institutional ownership of Masimo Corporation stands at 94.8%, held across 432 reporting institutions.
BlackRock, Inc. is the largest reported institutional holder of MASI, with approximately 4,644,578 shares worth $0.83B as of Q1 2026.
No marquee "smart money" managers (Berkshire, Burry, ARK, Tiger Global, Pershing Square, Baupost, etc.) currently appear among the top 25 institutional holders of MASI.
Our composite Smart Money Score for MASI is 54 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
128 institutions opened new positions in MASI during Q1 2026, while 81 fully exited. 249 added to existing positions and 53 trimmed.
MASI institutional ownership rose by 22.87 percentage points quarter-over-quarter, with a net change of +47 holders.
The top 10 institutions account for 53.8% of all reported 13F value in MASI, and the top 25 account for 70.6%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Masimo Corporation (MASI) Institutional Ownership