MASON CAPITAL MANAGEMENT LLC
Long book
$612.9M
Q1 2026
Positions
7
Top-10 weight
100%
concentration
Last quarter
+1.8%
SPY +14.8%
Turnover
55%
of book per quarter
Strategy in plain words
auto-generated from filingsMASON CAPITAL MANAGEMENT LLC is a diversified fundamental manager, specialised in industrials (76% of the long book), running a $612.9M US long book across 7 positions.
The portfolio is extremely concentrated — the top 10 positions are almost the whole book. Turnover is high — positions rotate quickly, so individual names matter less than the process. Current anchor positions: ATS CORP, ENVIRI CORP, BROOKDALE SENIOR LIVING INC, CLEAR CHANNEL OUTDOOR HOLDIN, READY CAPITAL CORP.
Over the last 9 quarters its long book ran on average 4.4pp per quarter behind the S&P 500, beating the index in 4 of 9 quarters. We rate its filings as signal-bearing: position changes reflect genuine views.
Implied long-book return vs S&P 500
methodology: positions priced quarterly, no shorts/options Fund long book S&P 500
Q1 2024
-3.9%
Q2 2024
-9.1%
Q3 2024
+3.8%
Q4 2024
-18.3%
Q1 2025
+27.2%
Q2 2025
-16.6%
Q3 2025
+7.5%
Q4 2025
+8.3%
Q1 2026
+1.8%
Sector allocation
Industrials 76%
Utilities 15%
Healthcare 5%
Services media 4%
Other 0%
Long book by quarter
What does MASON CAPITAL own?
Q1 2026 13F| Company | Sector | Shares | Value | % of book | Change |
|---|---|---|---|---|---|
| ATS ATS CORP | Industrials | 16.4M | $462.6M | 75.5% | +5.4% |
| NVRI ENVIRI CORP | Utilities | 4.5M | $88.2M | 14.4% | New |
| BKD BROOKDALE SENIOR LIVING INC | Healthcare | 2.2M | $30.6M | 5.0% | -37.7% |
| CCO CLEAR CHANNEL OUTDOOR HOLDIN | Services media | 9.8M | $23.3M | 3.8% | Held |
| JELD JELD-WEN HOLDING INC | Other | 776.9K | $963K | 0.2% | New |
| SBNY SIGNATURE BANK | — | 400.0K | $260K | 0.0% | Held |
13F filing history
| Period | Form | Filed | Entries | Reported value | Flags | Source |
|---|---|---|---|---|---|---|
| Q1 2026 | 13F-HR | May 15, 2026 | 7 | $612.9M | canonical | SEC ↗ |
| Q4 2025 | 13F-HR | Feb 17, 2026 | 9 | $561.6M | canonical | SEC ↗ |
| Q3 2025 | 13F-HR | Nov 14, 2025 | 6 | $491.4M | canonical | SEC ↗ |
| Q2 2025 | 13F-HR | Aug 14, 2025 | 4 | $511.5M | canonical | SEC ↗ |
| Q1 2025 | 13F-HR | May 15, 2025 | 5 | $427.2M | canonical | SEC ↗ |
| Q4 2024 | 13F-HR | Feb 14, 2025 | 4 | $470.5M | canonical | SEC ↗ |
| Q3 2024 | 13F-HR | Nov 14, 2024 | 6 | $502.6M | canonical | SEC ↗ |
| Q2 2024 | 13F-HR | Aug 14, 2024 | 6 | $538.2M | canonical | SEC ↗ |
| Q1 2024 | 13F-HR | May 15, 2024 | 6 | $727.8M | canonical | SEC ↗ |