William Blair & Company
AMTM

William Blair & Company’s Amentum Holdings AMTM Stock Holding History

William Blair & Company’s Portfolio AMTM Stock Details AMTM Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2026
Q2 		$564K Sell
27,278
-22,020
-45% -$533K ﹤0.01% 1183
2026
Q1 		$1.29M Sell
49,298
-30,667
-38% -$962K ﹤0.01% 861
2025
Q4 		$2.32M Buy
79,965
+29,316
+58% +$749K 0.01% 703
2025
Q3 		$1.21M Sell
50,649
-5,919
-10% -$144K ﹤0.01% 866
2025
Q2 		$1.34M Buy
56,568
+2,368
+4% +$49.5K ﹤0.01% 814
2025
Q1 		$986K Sell
54,200
-2,219
-4% -$45.2K ﹤0.01% 889
2024
Q4 		$1.19M Buy
56,419
+26,982
+92% +$697K ﹤0.01% 843
2024
Q3 		$949K Buy
+29,437
New +$839K ﹤0.01% 919

Other funds holding AMTM

AS
American Securities New York $3.75B AUM 23.12% 1-Year Est. Return
Invesco
Invesco Atlanta, Georgia $1.26T AUM 61.52% 1-Year Est. Return
BlackRock
BlackRock New York $6.73T AUM 46.02% 1-Year Est. Return
Primecap Management
Primecap Management Pasadena, California $169B AUM 114.72% 1-Year Est. Return
Vanguard Portfolio Management
Vanguard Portfolio Management Malvern, Pennsylvania $2.22T AUM
Vanguard Capital Management
Vanguard Capital Management Malvern, Pennsylvania $4.68T AUM
Fidelity Investments
Fidelity Investments Boston, Massachusetts $2.3T AUM 54.33% 1-Year Est. Return
Dimensional Fund Advisors
Dimensional Fund Advisors Austin, Texas $552B AUM 44.19% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $3.37T AUM 44.26% 1-Year Est. Return
FCM
Frontier Capital Management Boston, Massachusetts $10.7B AUM 67.78% 1-Year Est. Return

William Blair & Company's AMTM Position: Q2 2026 in Review

William Blair & Company reduced its Amentum Holdings (AMTM) stake by 45% in Q2 2026, selling an estimated $533K and leaving 27,278 shares worth $564K. The position accounts for ﹤0.01% of the portfolio, ranked #1183.

William Blair & Company first reported a position in AMTM in Q3 2024 and has held it in 8 quarters since. The position peaked at $2.32M in Q4 2025. 462 funds tracked by Wall St. Rank hold AMTM as of Q2 2026.

  • William Blair & Company held 27,278 shares of Amentum Holdings worth $564K as of Q2 2026.
  • William Blair & Company sold 22,020 Amentum Holdings shares in Q2 2026, an estimated $533K.
  • Amentum Holdings made up ﹤0.01% of William Blair & Company's portfolio in Q2 2026, its #1183 holding.
  • William Blair & Company first reported a position in Amentum Holdings in Q3 2024 and has held it in 8 quarters since.
  • William Blair & Company's Amentum Holdings position peaked at $2.32M in Q4 2025.
  • 462 funds tracked by Wall St. Rank held Amentum Holdings as of Q2 2026.

Based on William Blair & Company's 13F filing for Q2 2026, filed 11 Aug 2026.