A 72-year-old woman was admitted with a sensation of compression and shortness of breath. A mass was detected in the right atrium (RA) by transthoracic echocardiography. Preoperative chest computed tomography showed an RA tumor measuring 30×24 mm in the lateral wall. We performed resection under the cardiopulmonary bypass. Histopathological examination confirmed that this tumor was a lipoma.