Amentum Holdings, Inc.
Amentum Holdings, Inc. (AMTM) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · AMTM · as of Mar 31, 2025
Ownership Breakdown
444
Institutional Holders
▼ 29 vs Q4
$3.49B
Total Inst. Value
▼ $253,453 vs Q4
244.09M
Shares Outstanding
freeFloat 80.64%
191.79M
13F Shares Held
▲ 26.37M vs Q4
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
AMTM largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
AMERICAN SECURITIES LLC services-business services, nec | 43.89M | 18.06% | 18.06% | $798.87B | May 12, 2025 | — held |
BLACKROCK, INC. services-business services, nec | 18.25M | 7.51% | 7.51% | $332.13B | May 2, 2025 | ▲ 1.47M |
INVESCO LTD. services-business services, nec | 17.19M | 7.07% | 7.07% | $312.88B | May 12, 2025 | ▲ 3.33M |
VANGUARD GROUP INC services-business services, nec | 16.34M | 6.73% | 6.73% | $297.43B | May 9, 2025 | ▼ 199.9K |
PRIMECAP MANAGEMENT CO/CA/ services-business services, nec | 10.06M | 4.14% | 4.14% | $183.12B | May 9, 2025 | ▲ 3.65M |
STATE STREET CORP services-business services, nec | 6.58M | 2.71% | 2.71% | $119.69B | May 15, 2025 | ▲ 122.1K |
FMR LLC services-business services, nec | 4.41M | 1.81% | 1.81% | $80.24B | May 12, 2025 | ▲ 2.01M |
FRONTIER CAPITAL MANAGEMENT CO LLC services-business services, nec | 3.58M | 1.47% | 1.47% | $65.13B | May 15, 2025 | NEW |
THOMPSON SIEGEL & WALMSLEY LLC services-business services, nec | 3.33M | 1.37% | 1.37% | $60.54B | May 9, 2025 | ▲ 1.38M |
KOVITZ INVESTMENT GROUP PARTNERS, LLC services-business services, nec | 3.08M | 1.27% | 1.27% | $55.97B | May 19, 2025 | ▼ 77.0K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
36
Increased
+30.16M shares4
New Positions
first time holders9
Decreased
−3.77M shares0
Sold Out
fully exitedNet shares change (top 50)
+26.39M
+30.16M / −3.77M
Net new holders
+31
4 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
AMTM insider trading · insider activity
Source: SEC Form 4
5
Buy transactions
10
Sell transactions
0.50
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Heller John E. Chief Executive Officer | May 6, 2026 | Tax Withhold | 8,184 | $24.89 | $203.7K | 376.0K | Form 4 ↗ |
Mullen Sean Thomas Chief Growth Officer | May 6, 2026 | Tax Withhold | 2,762 | $24.89 | $68.7K | 32.4K | Form 4 ↗ |
Johnson Travis Barton Chief Financial Officer | May 6, 2026 | Tax Withhold | 4,097 | $24.89 | $102.0K | 118.2K | Form 4 ↗ |
Bruning Jill L Chief Technology Officer | May 6, 2026 | Tax Withhold | 2,731 | $24.89 | $68.0K | 197.5K | Form 4 ↗ |
Arnette Stephen A Chief Operating Officer | May 6, 2026 | Tax Withhold | 3,314 | $24.89 | $82.5K | 106.7K | Form 4 ↗ |
Bruning Jill L Chief Technology Officer | Mar 4, 2026 | Gift | 30,000 | — | — | 191.0K | Form 4 ↗ |
Arnette Stephen A Chief Operating Officer | Mar 2, 2026 | Tax Withhold | 750 | $30.70 | $23.0K | 96.4K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Amentum Holdings, Inc. (AMTM) is primarily owned by institutional investors, who hold approximately 78.6% of total shares outstanding. Company insiders own approximately 19.36%, while retail and public investors account for the remaining 2.06%.
The largest institutional shareholder of Amentum Holdings, Inc. is AMERICAN SECURITIES LLC, holding approximately 43.89 million shares — equal to 18.06% of outstanding shares — as of March 31, 2025.
A total of 444 institutional investors currently hold AMTM stock, with a combined institutional value of approximately $3.49 billion as of the most recent 13F filing period.
Frequently asked questions
AMTM ownershipAmentum Holdings, Inc. (AMTM) is primarily owned by institutional investors, who hold approximately 78.6% of shares. The largest shareholder is AMERICAN SECURITIES LLC with a 18.06% stake. Company insiders hold 19.36%. Data sourced from SEC Form 13F as of March 31, 2025.