Skip to content
Disclosery

MASON CAPITAL MANAGEMENT LLC

Follow

13F filer, CIK 1218735, NEW YORK, NY

MASON CAPITAL MANAGEMENT LLC reported $612,852,905 across 7 holdings for the quarter ended 2026-03-31, in a 13F-HR filed 2026-05-15.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001104659-26-062410

Period
2026-03-31
Reported value
$613M
Holdings
7
Top 10 weight
100%
New
2
Sold out
4

Largest buys vs the previous quarter

SecurityShares changeApprox. value
NVRInew+4,494,536$88.2M
ATSadded+840,602$23.7M
JELDnew+776,885$963K
RCadded+543,794$881K

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Largest sells vs the previous quarter

SecurityShares changeApprox. value
SOLSexited-633,801-$30.8M
JBSexited-1,306,000-$18.8M
BKDreduced-1,352,200-$18.5M
BORRexited-2,182,136-$8.79M
MLABexited-70,300-$5.52M

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Holdings, Q1 2026

Share positions as resolved from 13F-HR 0001104659-26-062410, largest first. % of portfolio is the value over $612,592,905, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
ATSATS CORPORATIONQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: 14,914,765 shares; 2024Q4: 14,914,765 shares; 2025Q1: 15,563,568 shares; 2025Q2: 15,563,568 shares; 2025Q3: 15,563,568 shares; 2025Q4: 15,563,568 shares; 2026Q1: 16,404,170 shares 16,404,170$463M75.51%+840,602Timeline
NVRIENVIRI CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: 4,494,536 shares 4,494,536$88.2M14.4%newTimeline
BKDBROOKDALE SR LIVING INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: 2,475,964 shares; 2025Q4: 3,585,941 shares; 2026Q1: 2,233,741 shares 2,233,741$30.6M4.99%-1,352,200Timeline
CCOCLEAR CHANNEL OUTDOOR HLDGSQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: 9,828,401 shares; 2024Q4: 9,828,401 shares; 2025Q1: 9,828,401 shares; 2025Q2: 9,828,401 shares; 2025Q3: 9,828,401 shares; 2025Q4: 9,828,401 shares; 2026Q1: 9,828,401 shares 9,828,401$23.3M3.8%0Timeline
RCREADY CAPITAL CORPQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: 838,856 shares; 2024Q4: 278,856 shares; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: 3,776,139 shares; 2026Q1: 4,319,933 shares 4,319,933$7M1.14%+543,794Timeline
JELDJELD-WEN HLDG INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: not reported; 2025Q3: not reported; 2025Q4: not reported; 2026Q1: 776,885 shares 776,885$963K0.16%newTimeline
SBNYSIGNATURE BANKQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q2: restricted; 2024Q3: 400,000 shares; 2024Q4: 400,000 shares; 2025Q1: 400,000 shares; 2025Q2: 400,000 shares; 2025Q3: 400,000 shares; 2025Q4: 400,000 shares; 2026Q1: 400,000 shares 400,000$260K0Value about 1/1,000 of the price other filers imply, kept as filed and left out of ratios.Timeline

Sold out in Q1 2026

Positions in the previous quarter's report that this quarter's report no longer lists.

SecurityShares beforeValue beforeType
SOLSSOLSTICE ADVANCED MATLS INC633,801$30.8Mshares
JBSJBS N.V.1,306,000$18.8Mshares
BORRBORR DRILLING LTD2,182,136$8.79Mshares
MLABMESA LABS INC70,300$5.52Mshares

How Q1 2026 was built

Available 13F filings of this filer for the quarter and their roles: the base report is the latest original or restatement, NEW HOLDINGS amendments filed after it are added (method).

FilingRoleAmendmentFiledAcceptedIngested
13F-HR 0001104659-26-062410 base2026-05-15acceptance time not in the bulk data set