Cor triatriatum is a rare congenital anomaly where the left or right atrium is subdivided by a thin membrane, resulting in three atrial chambers. We present a case of 55 years old female who presented progressive dyspnea with perpheral cyanosis. In a TEE and CT threeatrial heart was seen, with a thin- walled membrane across the LA dividing it into two compartments, one receiving the pulmonary venous flow and a true left atrium that connects to the left ventricle through mitral valve. JRCD 2015; 2 (3): 82–84