BlackRock Portfolio Management LLC reports beneficial ownership of 116,871 shares of Masimo Corp Common Stock, equal to 0.2% of the class as of 03/31/2026. The filing states BlackRock has sole voting power over 94,486 shares and sole dispositive power over 116,871 shares. The Schedule 13G/A is an amendment (Amendment No. 2) and is signed by Spencer Fleming, Managing Director, on 04/30/2026.
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Insights
BlackRock reports a small passive stake of 116,871 shares (0.2%).
BlackRock Portfolio Management LLC amends its Schedule 13G to show beneficial ownership of 116,871 shares of Masimo Common Stock with 94,486 shares subject to sole voting power as of 03/31/2026. The filing is dated and executed on 04/30/2026.
Because the reported stake is below 5%, this filing represents routine passive institutional reporting. Subsequent institutional filings or material disclosures could change the ownership picture; any change would be visible through later amendments.
Key Figures
Beneficial ownership:116,871 sharesPercent of class:0.2%Sole voting power:94,486 shares+2 more
5 metrics
Beneficial ownership116,871 sharesAmount beneficially owned as of <date>03/31/2026</date>
Percent of class0.2%Percent of Masimo Common Stock reported in Item 4
Sole voting power94,486 sharesNumber of shares with sole power to vote reported in Item 4
Sole dispositive power116,871 sharesNumber of shares with sole power to dispose reported in Item 4
Schedule 13G/A, Beneficial ownership, Sole dispositive power
3 terms
Schedule 13G/Aregulatory
"Amendment No. 2 ) MASIMO CORP Common Stock"
A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.
Beneficial ownershipfinancial
"Amount beneficially owned: 116,871 (b) Percent of class: 0.2%"
Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.
Sole dispositive powerfinancial
"Sole power to dispose or to direct the disposition of: 116,871"
Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 2)
MASIMO CORP
(Name of Issuer)
Common Stock
(Title of Class of Securities)
574795100
(CUSIP Number)
03/31/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
574795100
1
Names of Reporting Persons
BlackRock Portfolio Management LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
94,486.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
116,871.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
116,871.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0.2 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
MASIMO CORP
(b)
Address of issuer's principal executive offices:
52 DISCOVERY, IRVINE, CALIFORNIA, 92618
Item 2.
(a)
Name of person filing:
BlackRock Portfolio Management LLC
In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)
Address or principal business office or, if none, residence:
BlackRock Portfolio Management LLC, 50 Hudson Yards New York, NY 10001
(c)
Citizenship:
See Item 4 of Cover Page
(d)
Title of class of securities:
Common Stock
(e)
CUSIP No.:
574795100
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
116,871
(b)
Percent of class:
0.2%
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
94,486
(ii) Shared power to vote or to direct the vote:
0
(iii) Sole power to dispose or to direct the disposition of:
116,871
(iv) Shared power to dispose or to direct the disposition of:
0
Item 5.
Ownership of 5 Percent or Less of a Class.
Ownership of 5 percent or less of a class
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of MASIMO CORP. No one person's interest in the common stock of MASIMO CORP is more than five percent of the total outstanding common shares.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.
See Exhibit 99
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
What stake does BlackRock (MASI) report in the Schedule 13G/A?
BlackRock Portfolio Management LLC reports 116,871 shares, representing 0.2% of Masimo Corp common stock as of 03/31/2026. The filing is an amendment (Amendment No. 2) signed on 04/30/2026.
How much voting power does BlackRock state it holds in MASI?
The filing states BlackRock has sole voting power over 94,486 shares and no shared voting power. Voting and dispositive power figures are reported in Item 4 of the Schedule 13G/A.
Does this Schedule 13G/A indicate active control or more than 5% ownership?
No. The filing classifies the position as ownership of 5 percent or less of the class and reports a 0.2% stake, which is consistent with passive institutional reporting rather than active control.
Who signed the amendment and when was it signed?
The amendment is signed by Spencer Fleming, Managing Director, with a signature date of 04/30/2026, as shown on the Schedule 13G/A cover information.
What address is listed for BlackRock Portfolio Management LLC in the filing?
The filing lists the business address as 50 Hudson Yards, New York, NY 10001 for BlackRock Portfolio Management LLC in Item 2(b) of the Schedule 13G/A.
