As of November 10, 2026, 2 holders' latest Schedule 13D or 13G filings report owning 5% or more of Masimo Corp. The largest reported stake is Joe Kiani's, at 6.5%. 13 filings are on record since August 12, 2025 (Schedule 13G/A, May 14, 2026).
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Key facts
- · Reporting person: Pentwater Capital Management LP · Sole voting: 0 · Shared voting: 0 · Sole dispositive: 0 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: Politan Capital Management LP · Sole voting: 0 · Shared voting: 0 · Sole dispositive: 0 · Shared dispositive: 0 · SCHEDULE 13D/A, 2026-06-11
- · Holder: Pentwater Capital Management LP · Percent: 6.1% · SCHEDULE 13G
- · Holder: Barclays PLC · Percent: 5.54% · SCHEDULE 13G
- · Holder: Joe Kiani · Percent: 6.5% · SCHEDULE 13G/A
Masimo Corp has 13 Schedule 13D or 13G filings on record since 2025-08-12. 2 holders' latest filing reports 5% or more of common stock, par value $0.001 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| 6.5% | 3,657,039 | SCHEDULE 13G/A, 2026-05-14 | 2026-03-31 | |
| Barclays PLC | 5.54% | 2,892,262 | SCHEDULE 13G, 2026-05-14 | 2026-03-31 |
| Fmr LLC | 4.5% | 2,349,975 | SCHEDULE 13G/A, 2026-03-06 | 2026-02-27 |
| BlackRock Portfolio Management LLC | 0.2% | 116,871 | SCHEDULE 13G/A, 2026-04-30 | 2026-03-31 |
| Politan Capital Management LP | 0% | 0 | SCHEDULE 13D/A, 2026-06-11 | 2026-06-10 |
| The Vanguard Group | 0% | 0 | SCHEDULE 13G/A, 2026-03-27 | 2026-03-13 |
| Pentwater Capital Management LP | 0% | 0 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
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Keep reading
More on Masimo Corp and the records around it.
Masimo Corp elsewhere on the record
- Acquisition Jun 2026
Companies that share a holder
- Pentwater Capital Management LP also filed stake reports on 20 other companies: AMC Entertainment Holdings, Inc. (Aug 2026), Caesars Entertainment, Inc. (Aug 2026), Centessa Pharmaceuticals plc (Aug 2026)
- Barclays PLC also filed stake reports on 116 other companies: BIGLARI HOLDINGS INC-B (Nov 2026), CABLE ONE INC (Nov 2026), CALISA ACQUISITION CORP (Nov 2026)
- BlackRock Portfolio Management LLC also filed stake reports on 118 other companies: AMERISAFE INC (Nov 2026), BlackRock ETF Trust (Nov 2026), iShares J.P. Morgan EM Local Currency Bond ETF (Nov 2026)
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What the Full Report on Masimo Corp covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Politan Capital Management LP | 0 | 0 | 0 | 0 | SCHEDULE 13D/A, 2026-06-11 |
| Politan Capital Management GP LLC | 0 | 0 | 0 | 0 | SCHEDULE 13D/A, 2026-06-11 |
| Politan Capital Partners GP LLC | 0 | 0 | 0 | 0 | SCHEDULE 13D/A, 2026-06-11 |
| Quentin Koffey | 0 | 0 | 0 | 0 | SCHEDULE 13D/A, 2026-06-11 |
| Pentwater Capital Management LP | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| Matthew Halbower | 0 | 0 | 0 | 0 | SCHEDULE 13G/A, 2026-08-14 |
The latest filing identifies Masimo Corp by CUSIP 574795100 and gives its principal executive office as 52 DISCOVERY, IRVINE, CA 92618 (SCHEDULE 13G/A, 2026-08-14).
Purpose of Transaction (Item 4)
Politan Capital Management LP
Item 4 is hereby amended and supplemented as follows: On June 10, 2026 (the "Closing Date"), the Merger was consummated pursuant to the Merger Agreement. At the effective time of the Merger (the "Effective Time"), Merger Sub merged with and into the Issuer, with the Issuer continuing as the surviving corporation and a wholly owned subsidiary of Parent. At the Effective Time, each share of Common Stock issued and outstanding immediately prior to the Effective Time (other than shares excluded or treated as described in the Merger Agreement) was automatically cancelled, extinguished and converted into the right to receive an amount in cash equal to $180.00 per share, without interest and less any applicable withholding taxes (the "Per Share Merger Consideration"). Accordingly, the 4,590,873 shares of Common Stock beneficially owned by the Reporting Persons immediately prior to the Effective Time were converted into the right to receive the Per Share Merger Consideration. In addition, the 1,119 restricted share units held by Mr. Koffey, as a non-employee director of the Issuer, were cancelled and converted at the Effective Time into the right to receive an amount in cash equal to the Per Share Merger Consideration for each share of Common Stock underlying such restricted share units. As a result of the Merger, the Reporting Persons ceased to beneficially own any shares of Common Stock.Item 4 of the SCHEDULE 13D/A filed 2026-06-11
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-12 | Joe Kiani | 11.4% | SCHEDULE 13G/A |
| 2025-11-12 | Joe Kiani | 11.1% | SCHEDULE 13G/A |
| 2026-01-21 | BlackRock Portfolio Management LLC | 8.2% | SCHEDULE 13G/A |
| 2026-02-13 | Joe Kiani | 10.3% | SCHEDULE 13G/A |
| 2026-02-17 | Politan Capital Management LP | 6.2% | SCHEDULE 13D/A |
| 2026-03-06 | Fmr LLC | 4.5% | SCHEDULE 13G/A |
| 2026-03-27 | The Vanguard Group | 0% | SCHEDULE 13G/A |
| 2026-04-30 | BlackRock Portfolio Management LLC | 0.2% | SCHEDULE 13G/A |
| 2026-05-14 | Barclays PLC | 5.54% | SCHEDULE 13G |
| 2026-05-14 | Joe Kiani | 6.5% | SCHEDULE 13G/A |
| 2026-05-15 | Pentwater Capital Management LP | 6.1% | SCHEDULE 13G |
| 2026-06-11 | Politan Capital Management LP | 0% | SCHEDULE 13D/A |
| 2026-08-14 | Pentwater Capital Management LP | 0% | SCHEDULE 13G/A |
Questions about who owns Masimo Corp
Who owns Masimo Corp?
On this page, 2 holders' latest ownership filings report 5% or more of Masimo Corp: Joe Kiani (6.5%, Schedule 13G/A, filed 2026-05-14) and Barclays PLC (5.54%, Schedule 13G, filed 2026-05-14).
Who are the largest shareholders of Masimo Corp?
By the share each holder's latest filing reports, the largest holders of Masimo Corp on this page are Joe Kiani (6.5%) and Barclays PLC (5.54%).
When did Joe Kiani buy into Masimo Corp?
The filings give report dates, not purchase dates. The earliest filing from Joe Kiani on this page is the Schedule 13G/A, filed 2025-08-12, reporting 11.4%; its latest, Schedule 13G/A filed 2026-05-14, reports 6.5%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 13 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Also on the record for Masimo Corp
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| June 10, 2026 | Acquired by Danaher Corporation | — | Acquisition | Source |
| June 10, 2026 | Leadership change filing (Form 8-K, Item 5.02) | — | Leadership changes | Source |
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.