Calcified amorphous tumor (CAT) is a non-neoplastic cardiac mass composed of nodules of calcium with a background of amorphous fibrous material and was first described in 1997. This report describes a 61-year-old man, who had been on hemodialysis for 10 years and was referred to our hospital with a diagnosis of acute myocardial infarction. He had percutaneous coronary intervention (PCI) for stenosis of the left anterior descending artery (LAD). He was hospitalized and under medical treatment. A follow-up echocardiogram was performed and revealed a normal ejection fraction of 0.60. Moderate mitral annular calcification with mild-to-moderate mitral stenosis was seen. An ultrasound-mobile mass was visualized in the left ventricular outflow tract (LVOT). There was no hemodynamic evidence of LVOT obstruction on Doppler echocardiography. Transesophageal echocardiography showed a mobile mass attached to the LVOT in the mitral valve annulus that extended almost to the membranous septum. Due to the mobility of the mass and potential for embolism, surgical removal was advised. Concomitant procedures (coronary artery bypass grafting (CABG) and a full maze operation) were proposed because he still had symptoms of chest pain with myocardial ischemia and palpitations due to chronic atrial fibrillation. Surgery was performed through a median sternotomy on cardiopulmonary bypass. After aortic cross-clamping, the mass was approached through a horizontal incision in the ascending aorta. The white tumor was resected easily from the membranous septum. The operation was finished after CABG and a full maze procedure, and his clinical course was uneventful. Histological examination showed that the tumor contained many calcified nodules and fibrino-sanguineous deposits ; these findings are compatible with CAT.