While a 74-year-old man with a past history of cerebral infarction was undergoing surface echocardiography due to transient atrial fibrillation, an unstable, pedunculated tumor was detected in the left ventricular outflow tract. As the results of transesophageal echocardiography suggested a left ventricular tumor, semi-emergency surgery was performed. Based on pathological findings, the tumor was diagnosed as papillary fibroelastoma. This tumor mainly affects the cardiac valves and is often discovered during open-heart surgery or autopsy. This report presents a very rare case of preoperatively identified papillary fibroelastoma in the left ventricular outflow tract.