MASON CAPITAL MANAGEMENT LLC
CIK
1218735
Location
New York, NY
Portfolio Value
Small
$524,410,108
Diversification
Highly concentrated
Filing Date
Global Rank
#2,546
/ 8,605
▼ 51
· as of Mar 2026
Top Industry
Specialty Industrial Machinery
88.2%
3Y Alpha vs SPY
-30.4%
Period ended 3 months ago
Filed May 15, 2026 · 55d
25 quarters · since Mar 2020
Clone Performance
Jul 2023–Jul 2026 · vs SPYHypothetical growth of cloning every reported 13F position and rebalancing on each filing, indexed to the same start.
Cloned portfolio
-25.9%
SPY
+76.5%
Annualised alpha
-30.4%
Max drawdown
−52.2%
Estimate. 13F holdings are quarter-lagged and long-only, so the clone rebalances about 45 days after each period end — when the filing becomes public — and excludes options and short positions. Past performance does not predict future results.
Portfolio Concentration
6 positions · as of Mar 31, 2026 · Δ vs Dec 31, 2025Top Position
88.2%
+11.8 pts
Top 5
100.0%
+4.0 pts
Top 10
100.0%
0.0 pts
HHI
7,837
Highly concentrated+1,894
Portfolio Trend
25 quarters · across all stocks
Sector Breakdown
As of Mar 31, 2026| Sector | % Portfolio | Value |
|---|---|---|
| Industrials | 88.4% | $463,560,931 |
| Healthcare | 5.8% | $30,557,576 |
| Communication Services | 4.4% | $23,293,310 |
| Real Estate | 1.3% | $6,998,291 |
Last Quarter's Activity
Export CSVTrimmed
Positions the filer reduced
1 positions
| Ticker | Company | Δ Shares | Shares | Value | Open |
|---|---|---|---|---|---|
| BKD | Brookdale Senior Living Inc. | −1,352,200 | 2,233,741 | $30,557,576 | |
| No positions match the current search. | |||||
Sold Out
Positions the filer fully exited
4 positions
6 positions ·
$524,410,108 total
· as of Mar 31, 2026
| Ticker | Company | Type | Shares | Value (USD) | % of Portfolio | History |
|---|---|---|---|---|---|---|
| ATS |
ATS Corp /ATS
Industrials
|
Added | 16,404,170 | $462,597,594 | 88.21% | |
| BKD |
Brookdale Senior Living Inc.
Healthcare
|
Reduced | 2,233,741 | $30,557,576 | 5.83% | |
| CCO |
Clear Channel Outdoor Holdings, Inc.
Communication Services
|
Held | 9,828,401 | $23,293,310 | 4.44% | |
| RC |
Ready Capital Corp
Real Estate
|
Added | 4,319,933 | $6,998,291 | 1.33% | |
| JELD |
JELD-WEN Holding, Inc.
Industrials
|
NEW | 776,885 | $963,337 | 0.18% | |
| NVRI |
Enviri Corp
Industrials
|
NEW | 4,494,536 | $0 | 0.00% |