Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in ATS held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | MASON CAPITAL MANAGEMENT LLC | 16.4M | $462.6M | +5.4% | 16.721% | 75.48% |
| 2 | Turtle Creek Asset Management Inc. | 10.4M | $292.9M | +84.1% | 10.586% | 7.46% |
| 3 | ROYAL BANK OF CANADA | 7.8M | $218.9M | +1.5% | 7.912% | 0.04% |
| 4 | EdgePoint Investment Group Inc. | 7.2M | $202.1M | +4.0% | 7.307% | 1.62% |
| 5 | BANK OF MONTREAL /CAN/ | 3.1M | $87.8M | +3.1% | 3.175% | 0.03% |
| 6 | FAIRFAX FINANCIAL HOLDINGS LTD/ CAN | 2.5M | $69.4M | 0.0% | 2.534% | 3.57% |
| 7 | VANGUARD CAPITAL MANAGEMENT LLC | 2.4M | $66.7M | — | 2.412% | 0.00% |
| 8 | JANUS HENDERSON GROUP PLC | 2.3M | $64.5M | +166.6% | 2.341% | 0.03% |
| 9 | FMR LLC | 2.3M | $64.2M | +7.5% | 2.321% | 0.00% |
| 10 | Connor, Clark & Lunn Investment Management Ltd. | 2.3M | $63.8M | -8.9% | 2.308% | 0.15% |
| 11 | ACK Asset Management LLC | 1.8M | $52.1M | 0.0% | 1.882% | 6.50% |
| 12 | FIL Ltd | 1.8M | $50.1M | +3219.4% | 1.812% | 0.04% |
| 13 | TD Waterhouse Canada Inc. | 1.6M | $46.9M | +69.1% | 1.666% | 0.14% |
| 14 | Hill City Capital, LP | 1.6M | $46.5M | 0.0% | 1.682% | 1.66% |
| 15 | TD ASSET MANAGEMENT INC | 1.4M | $40.0M | +19.2% | 1.450% | 0.03% |
| 16 | Vinva Investment Management Ltd | 2.1M | $36.5M | — | 2.129% | 0.45% |
| 17 | KEMPEN CAPITAL MANAGEMENT N.V. | 863K | $33.9M | +5.9% | 0.880% | 0.30% |
| 18 | Scheer, Rowlett & Associates Investment Management Ltd. | 1.2M | $33.3M | -3.6% | 1.205% | 2.40% |
| 19 | Clearbridge Investments, LLC | 1.1M | $30.8M | -1.8% | 1.112% | 0.03% |
| 20 | Marathon Asset Management Ltd | 1.1M | $30.7M | -0.4% | 1.115% | 1.18% |
| 21 | BANK OF AMERICA CORP /DE/ | 946K | $26.7M | -14.0% | 0.964% | 0.00% |
| 22 | Alberta Investment Management Corp | 940K | $26.5M | -29.8% | 0.958% | 0.17% |
| 23 | MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. | 758K | $21.3M | -33.6% | 0.773% | 0.03% |
| 24 | MASSACHUSETTS FINANCIAL SERVICES CO /MA/ | 534K | $20.9M | -4.4% | 0.544% | 0.01% |
| 25 | VANGUARD FIDUCIARY TRUST CO | 728K | $20.5M | — | 0.742% | 0.01% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in ATS — a direct measure of their conviction.
Filings activity in ATS during Q1 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 126 | +5.9% | 88.27% | +9.42 pp | $2.37B | +12% |
| Q4 2025 | 119 | +4.4% | 78.85% | +4.39 pp | $2.12B | +5.9% |
| Q3 2025 | 114 | 12% | 74.46% | 18.84 pp | $2.00B | 20% |
| Q2 2025 | 129 | +7.5% | 93.30% | +19.95 pp | $2.51B | +27% |
| Q1 2025 | 120 | 5.5% | 73.35% | 15.92 pp | $1.97B | 18% |
| Q4 2024 | 127 | +0.0% | 89.27% | +4.42 pp | $2.40B | +5.2% |
| Q3 2024 | 127 | 3.1% | 84.85% | 9.12 pp | $2.28B | 9.7% |
| Q2 2024 | 131 | — | 93.97% | — | $2.52B | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying ATS stock.
Based on Q1 2026 13F filings, institutional ownership of ATS Corporation stands at 88.3%, held across 126 reporting institutions.
MASON CAPITAL MANAGEMENT LLC is the largest reported institutional holder of ATS, with approximately 16,404,170 shares worth $0.46B as of Q1 2026.
No marquee "smart money" managers (Berkshire, Burry, ARK, Tiger Global, Pershing Square, Baupost, etc.) currently appear among the top 25 institutional holders of ATS.
Our composite Smart Money Score for ATS is 50 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
24 institutions opened new positions in ATS during Q1 2026, while 17 fully exited. 71 added to existing positions and 30 trimmed.
ATS institutional ownership rose by 9.42 percentage points quarter-over-quarter, with a net change of +7 holders.
The top 10 institutions account for 67.2% of all reported 13F value in ATS, and the top 25 account for 89.0%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
ATS Corporation (ATS) Institutional Ownership