[SCHEDULE 13D/A] Mercury Systems Inc. SEC Filing

Rhea-AI Filing Summary

JANA Partners Management, LP amended its Schedule 13D for Mercury Systems Inc. (MRCY) to report beneficial ownership of 5,964,313 shares, equal to approximately 10.0% of the 59,915,670 shares outstanding as of July 31, 2025. The reported stake includes 4,832 deferred stock units (DSUs) granted to a director, which vest on the earlier of the first anniversary of the grant and the next annual meeting and convert to shares only when the director leaves the board; those DSUs have been assigned to JANA so settlement on vesting will be made to the Reporting Person.

The filing states JANA has sole voting and dispositive power over the reported shares and that recent transactions in the past 60 days were effected in the open market through various brokers; no other person is known to have rights to dividends or sale proceeds from these shares. This Amendment No. 2 updates Items 5 and 6 of the prior Schedule 13D.

Positive

• Material 10.0% stake disclosed, representing 5,964,313 shares which is sizeable and potentially influential
• Sole voting and dispositive power over the reported shares gives JANA clear control of voting decisions for this position
• Director-assigned DSUs have been assigned to JANA, ensuring settlement on vesting will be made to the Reporting Person

Negative

• None.

Insights

Activist / Securities Analyst

TL;DR: JANA now discloses a material ~10% stake in MRCY with sole voting power, signaling a potentially influential shareholder presence.

JANA Partners reports beneficial ownership of 5,964,313 shares, representing approximately 10.0% of outstanding Mercury Systems stock, which is a material position for a public company of this size. The filing confirms sole voting and dispositive power, implying JANA can unilaterally exercise voting rights for this block. Inclusion of 4,832 DSUs assigned from a director creates a contingent linkage to board compensation, though those DSUs convert to shares only upon the directors departure, so their immediate economic or voting effect is limited until vested and settled. Recent open-market purchases over the past 60 days are disclosed via Schedule A, indicating accumulation rather than a single block acquisition. For investors, the key takeaway is the emergence of a substantial activist-capable holder that could influence governance or strategic decisions.

Corporate Governance Specialist

TL;DR: Disclosure shows governance relevance because the stake includes director-assigned DSUs and JANA holds sole control over voting.

The assignment of DSUs from a board member to JANA ties a portion of director compensation to the Reporting Person and may reflect a cooperative relationship or pre-existing agreement regarding those awards. While vested DSUs do not convert until the director leaves the board, the assignment gives JANA entitlement to settlement upon vesting, which is noteworthy from a governance transparency perspective. The filing updates Items 5 and 6 and clarifies there are no other parties with rights to dividends or proceeds, concentrating economic and voting interests with JANA. This level of disclosure is standard but material, as a 10% holder with sole voting power can meaningfully affect shareholder votes and strategic choices.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

Mercury Systems Inc

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

589378108

(CUSIP Number)

Ele Klein & Adriana Schwartz
McDermott Will & Schulte LLP, 919 Third Avenue
New York, NY, 10022
212-756-2000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

08/13/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 589378108

1

Name of reporting person

JANA Partners Management, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 5,964,313.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 5,964,313.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

5,964,313.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

10.0 %

14

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.01 per share
(b)	Name of Issuer: Mercury Systems Inc
(c)	Address of Issuer's Principal Executive Offices: 50 Minuteman Road, Andover, MASSACHUSETTS , 01810.
Item 1 Comment: This Amendment No. 2 ("Amendment No. 2") amends and supplements the statement on Schedule 13D filed with the SEC on July 6, 2023 (as amended from time to time, the "Schedule 13D") with respect to the Shares of the Issuer. This Amendment No. 2 amends Items 5 and 6 as set forth below. Capitalized terms used herein and not otherwise defined in this Amendment No. 2 have the meanings set forth in the Schedule 13D.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5(a) of the Schedule 13D is hereby amended and restated in its entirety as follows: The aggregate percentage of Shares reported to be beneficially owned by the Reporting Person is based upon 59,915,670 Shares outstanding as of July 31, 2025, as reported in the Issuer's Annual Report on Form 10-K for the fiscal year ended June 27, 2025, filed with the SEC on August 11, 2025. As of the close of business on the date hereof, JANA may be deemed to beneficially own 5,964,313 Shares, representing approximately 10.0% of the Shares outstanding. This includes 4,832 deferred stock units ("DSUs") granted to Mr. Ostfeld on October 23, 2024 for his service on the Board of Directors of the Issuer (the "Board"). The DSUs vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into Shares until the date on which Mr. Ostfeld ceases to be a member of the Board. Mr. Ostfeld has assigned all rights to any Shares issuable pursuant to the grant to the Reporting Person. Pursuant to the assignment, settlement of the award on vesting will be made to the Reporting Person.
(b)	Item 5(b) of the Schedule 13D is hereby amended and restated in its entirety as follows: The Reporting Person has sole voting and dispositive power over 5,964,313 Shares, which power is exercised by the Principal.
(c)	Item 5(c) of the Schedule 13D is hereby amended and restated in its entirety as follows: Information concerning transactions in the Shares effected by the Reporting Person in the past sixty (60) days is set forth in Schedule A hereto and is incorporated herein by reference. All of the transactions in Shares listed herein were effected in the open market through various brokerage entities.
(d)	Item 5(d) of the Schedule 13D is hereby amended and restated in its entirety as follows: No person (other than the Reporting 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, the Shares.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Item 6 of the Schedule 13D is hereby amended and supplemented as follows: The information disclosed in Item 5(a) is incorporated herein by reference.

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.

JANA Partners Management, LP

Signature:	/s/ Jennifer Fanjiang
Name/Title:	Jennifer Fanjiang, Partner, Chief Legal Officer and Chief Compliance Officer
Date:	08/15/2025

FAQ

How many shares of MRCY does JANA Partners beneficially own?

5,964,313 shares, representing approximately 10.0% of the 59,915,670 shares outstanding as of July 31, 2025.

Does JANA Partners have voting control over its MRCY shares?

Yes. The filing states JANA has sole voting and dispositive power over the reported 5,964,313 shares.

What are the DSUs included in JANA's reported position?

4,832 deferred stock units (DSUs) granted to a director on October 23, 2024 are included; they vest on the earlier of the first anniversary of the grant and the next annual meeting and convert to shares when the director leaves the board.

Were the recent share transactions made in blocks or in the open market?

Open market purchases. The filing states all transactions in the past 60 days were effected in the open market through various brokerage entities and are listed in Schedule A.

Does anyone else have rights to dividends or sale proceeds from these shares?

No. The filing states no person other than the Reporting Person is known to have the right to receive dividends or proceeds from the sale of the reported shares.