A 37-year-old woman was evaluated for signs and symptoms of cardiac tamponade 11 days after mitral valve replacement and tricuspid valve repair. The transthoracic echocardiogram showed a large, compartmentalized pericardial effusion that resulted in left ventricular apical diastolic collapse. Also noted were right ventricular posterior wall diastolic collapse and hemodynamic findings consistent with cardiac tamponade. This case highlights the atypical echocardiographic findings in patients with pericardial effusions after cardiac surgery.