Single atrium (SA) is one of the rare congenital anomalies in which there is a complete absence of the atrial septum without an endocardial cushion defect associated with the absence of malformation of the atrioventricular (AV) valves. The term "common atrium" is used to denote the condition where there is a complete absence of the atrial septum or it is represented by a small strand of tissue present at the superior atrial wall of the common chamber, absence of interventricular communication, and accompanying AV cushion defect. Our patient demonstrated typical echocardiographic features of three-chambered heart (SA), which is a rare entity.