A 46-year-old woman underwent pericardiocentesis and pericardial window for recurrent pericardial effusion. She presented 17 months later with signs and symptoms consistent with constrictive pericarditis. Cardiac magnetic resonance imaging revealed an infiltrative mass surrounding the pericardium. A transcutaneous core needle biopsy of the pericardium confirmed the diagnosis of pericardial mesothelioma.