Unroofed coronary sinus, an unusual form of interatrial communication, is a rare cardiac anomaly. It is not a true defect of the atrial septum. It is described as a partial (focal or fenestrated) or complete absence of the roof of the coronary sinus, resulting in a communication between the coronary sinus and left atrium. It is presumably the least common variety of defects associated with interatrial shunting. Such defects are often difficult to diagnose and may even be overlooked during surgery for complex congenital heart disease. In most cases, they are associated with a persistent left superior vena cava, pulmonary or tricuspid atresia, and hearts with isomeric right atrial appendages. We report a case of this unusual form of interatrial communication without any associated anomalies in a 7-year-old girl child who presented to us with exertional dyspnea.