Masimo Corporation
Masimo Corporation (MASI) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · MASI · as of Sep 30, 2025
Ownership Breakdown
364
Institutional Holders
▼ 19 vs Q2
$8.29B
Total Inst. Value
▼ $1.39B vs Q2
52.37M
Shares Outstanding
freeFloat 84.61%
56.18M
13F Shares Held
▼ 1.35M vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
MASI largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
BLACKROCK, INC. electromedical & electrotherapeutic apparatus | 10.36M | 19.19% | 19.19% | $1.53T | Nov 12, 2025 | ▼ 146.2K |
FMR LLC electromedical & electrotherapeutic apparatus | 8.21M | 15.21% | 15.21% | $1.21T | Nov 13, 2025 | ▲ 32.3K |
VANGUARD GROUP INC electromedical & electrotherapeutic apparatus | 4.81M | 8.91% | 8.91% | $709.72B | Nov 7, 2025 | ▲ 171.9K |
POLITAN CAPITAL MANAGEMENT LP electromedical & electrotherapeutic apparatus | 4.59M | 8.50% | 8.50% | $677.20B | Nov 14, 2025 | ▼ 126.9K |
MASSACHUSETTS FINANCIAL SERVICES CO /MA/ electromedical & electrotherapeutic apparatus | 2.62M | 4.85% | 4.85% | $386.58B | Oct 29, 2025 | ▲ 149.6K |
T. ROWE PRICE INVESTMENT MANAGEMENT, INC. electromedical & electrotherapeutic apparatus | 2.13M | 3.94% | 3.94% | $313.80B | Nov 14, 2025 | ▼ 373.4K |
CAPITAL RESEARCH GLOBAL INVESTORS electromedical & electrotherapeutic apparatus | 1.85M | 3.43% | 3.43% | $273.58B | Nov 13, 2025 | ▼ 1.5K |
STATE STREET CORP electromedical & electrotherapeutic apparatus | 1.48M | 2.75% | 2.75% | $219.03B | Nov 14, 2025 | ▼ 1.9K |
WESTFIELD CAPITAL MANAGEMENT CO LP electromedical & electrotherapeutic apparatus | 1.42M | 2.63% | 2.63% | $209.41B | Nov 12, 2025 | ▲ 238.0K |
ALYESKA INVESTMENT GROUP, L.P. electromedical & electrotherapeutic apparatus | 1.38M | 2.56% | 2.56% | $203.78B | Nov 17, 2025 | ▲ 246.6K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
30
Increased
+3.24M shares2
New Positions
first time holders17
Decreased
−1.90M shares0
Sold Out
fully exitedNet shares change (top 50)
+1.35M
+3.24M / −1.90M
Net new holders
+15
2 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
MASI insider trading · insider activity
Source: SEC Form 4
13
Buy transactions
9
Sell transactions
1.44
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Scannell Timothy J director | Apr 23, 2026 | Award | 1,119 | — | — | 2.2K | Form 4 ↗ |
LANE WENDY E director | Apr 23, 2026 | Award | 1,119 | — | — | 2.2K | Form 4 ↗ |
Brennan Michelle Chairman of the Board | Apr 23, 2026 | Award | 1,119 | — | — | 2.2K | Form 4 ↗ |
Hellmann Elisabeth A Chief Human Resources Officer | Apr 21, 2026 | Tax Withhold | 121 | $178.43 | $21.6K | 214 | Form 4 ↗ |
Szyman Catherine M. CEO | Mar 11, 2026 | Tax Withhold | 1,069 | $175.47 | $187.6K | 7.6K | Form 4 ↗ |
Young Micah W EVP & Chief Financial Officer | Mar 11, 2026 | Tax Withhold | 471 | $175.47 | $82.6K | 25.7K | Form 4 ↗ |
Politan Capital Management LP Director by deputization | Mar 11, 2026 | J-Other | 142,681 | — | — | 142.7K | Form 4 ↗ |
Politan Capital Management LP Director by deputization | Mar 12, 2026 | J-Other | 130,869 | — | — | 130.9K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Masimo Corporation (MASI) is primarily owned by institutional investors, who hold approximately 100.0% of total shares outstanding. Company insiders own approximately 15.39%, while retail and public investors account for the remaining 0.00%.
The largest institutional shareholder of Masimo Corporation is BLACKROCK, INC., holding approximately 10.36 million shares — equal to 19.19% of outstanding shares — as of September 30, 2025.
A total of 364 institutional investors currently hold MASI stock, with a combined institutional value of approximately $8.29 billion as of the most recent 13F filing period.
Frequently asked questions
MASI ownershipMasimo Corporation (MASI) is primarily owned by institutional investors, who hold approximately 100.0% of shares. The largest shareholder is BLACKROCK, INC. with a 19.19% stake. Company insiders hold 15.39%. Data sourced from SEC Form 13F as of September 30, 2025.