Cor triatriatum associated with situs inversus is rare. A 6-month-old male who had cor triatriatum with atrial septal defect (ASD) and situs inversus totalis was successfully operated. Urgent surgical intervention was performed because of congestive cardiac failure despite drug therapy. The abnormal septum in the left atrium was resected and ASD was closed. His postoperative course has been uneventful.