A 68-year-old man with acute chest pain was transported into the emergency room in our hospital. He was in shock, with a systolic blood pressure of 63 mmHg and a heart rate of 115 beats per minute. Echocardiography revealed a cardiac tamponade, but no signs of acute aortic dissection were found by computed tomography. He immediately underwent pericardial fluid drainage and was transferred to the operation theatre. Pericardiotomy was performed and hemorrhage from the right atrium was found. Then, a mass of 35 mm in diameter was also detected by transesophageal echocardiography. Resection of the right atrial tumor was performed under cardiopulmonary bypass. A bovine pericardial patch was used for the repair of the defect in the right atrium. The pathological diagnosis was cardiac hemangioma with no malignant signs.