Mason Capital Management LLC 13F holdings, Q4 2025
Holdings as of December 31, 2025 · filings on SEC EDGAR · latest filing →
Mason Capital Management LLC disclosed 9 US equity positions worth $561.6m in its Q4 2025 13F filing. The largest position was ATS at 76.3% of the reported book, followed by BKD and SOLS. Against the Q3 2025 filing, it opened 4 new positions, added to 1 and reduced 0 among the top 9 holdings.
What did Mason Capital Management LLC own in Q4 2025? Top 9 positions
| # | Stock | Sector | Weight | Value | Shares | Δ shares | vs Q3 2025 |
|---|---|---|---|---|---|---|---|
| 1 | ATS ATS CORPORATION | 76.3% | $428.6m | 15,563,568 | 0% | held | |
| 2 | BKD BROOKDALE SENIOR LIVING INC | Healthcare | 6.9% | $38.7m | 3,585,941 | 45% | added |
| 3 | SOLS SOLSTICE ADV MATERIALS INC | Basic Materials | 5.5% | $30.8m | 633,801 | – | new |
| 4 | CCO CLEAR CHANNEL OUTDOOR HLDGS | Communication Services | 3.9% | $21.7m | 9,828,401 | 0% | held |
| 5 | JBS JBS N.V. | Consumer Defensive | 3.4% | $18.8m | 1,306,000 | – | new |
| 6 | BORR BORR DRILLING LTD | Energy | 1.6% | $8.8m | 2,182,136 | – | new |
| 7 | RC READY CAPITAL CORP | 1.5% | $8.2m | 3,776,139 | – | new | |
| 8 | MLAB MESA LABORATORIES INC | Technology | 1.0% | $5.5m | 70,300 | 0% | held |
| 9 | SBNY SIGNATURE BANK | Financial Services | 0.1% | $404.0k | 400,000 | 0% | held |
Weights are shares of the reported long US equity book (options excluded). Values are as filed, normalised to whole dollars. Share changes compare against the immediately preceding filing only.