Vanguard Portfolio Management filed an amended beneficial ownership statement with the SEC on October 30, 2026, disclosing a 4.99% stake in Mercury Systems Inc as of September 30, 2026.

Key Highlights

  • Aggregate beneficial ownership: Vanguard Portfolio Management reported beneficial ownership of 3,038,957 shares of Mercury Systems Inc common stock, representing 4.99% of the class.
  • Sole dispositive power: Vanguard Portfolio Management holds sole power to dispose of all 3,038,957 shares, according to the filing.
  • Sole voting power: The filing indicates sole voting power over 51,923 shares, with shared voting power reported as zero.
  • Triggering event date: The date of event requiring the filing was September 30, 2026.
  • Affiliates included: The filing covers securities beneficially owned by Vanguard Portfolio Management LLC and affiliates Vanguard Fiduciary Trust Company and Vanguard Global Advisers, LLC.
  • Amendment: This statement is Amendment No. 1 to a prior filing, signed by My Trieu-Gatt, Authorized Signatory and Head of Global Fund Administration.

Vanguard Portfolio Management's Disclosed Position in Mercury Systems

According to the filing, Vanguard Portfolio Management, organized in Pennsylvania and headquartered at 100 Vanguard Blvd, Malvern, PA 19355, reported aggregate beneficial ownership of 3,038,957 shares of Mercury Systems Inc common stock. The reported stake equals 4.99% of the class, placing it within the threshold addressed in Item 5 of the filing, which the statement characterizes as "ownership of 5 percent or less of a class." Mercury Systems Inc, the issuer, is a defense electronics company with principal executive offices at 50 Minuteman Road, Andover, MA 01810, and its common stock trades on NASDAQ:MRCY.

The filing specifies that Vanguard Portfolio Management holds sole dispositive power over all 3,038,957 shares, while sole voting power extends to only 51,923 shares. Shared voting power and shared dispositive power are each reported as zero. The statement notes that the filing encompasses securities held by Vanguard funds and managed accounts, including investment companies registered under the Investment Company Act of 1940, over which the reporting entity or its listed affiliates exercise dispositive and/or voting power. The filing also states that no single other person's interest in the reported securities exceeds 5%.

The certification included in the filing, signed by My Trieu-Gatt as Authorized Signatory and Head of Global Fund Administration, states that the securities "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."

What Was Disclosed

Vanguard Portfolio Management filed Amendment No. 1 to its beneficial ownership statement on October 30, 2026, reporting 3,038,957 shares, or 4.99%, of Mercury Systems Inc common stock as of September 30, 2026, with full sole dispositive power and limited sole voting power over 51,923 shares.