A 64-year-old female was admitted with general fatigue and orthopnea. Preoperative echocardiography showed a free ball thrombus in the left atrium, mitral stenosis and severe tricuspid regurgitation. To avoid a herniation of thrombus to the mitral orifice, an emergency operation was performed. Two free and small mural thrombi were found in the left atrium. Thrombectomy, mitral valve replacement and tricuspid annuloplasty were performed successfully. Postoperative course was uneventful, and she was discharged in good condition on the 21st postoperative day.