Heart failure in early infancy is commonly caused by lesions leading to pulmonary over circulation secondary to left-to-right shunt. This case report describes an unusual cause of significant left-to-right shunt in a 2 months old infant presenting with congestive heart failure, which was diagnosed with transthoracic echocardiography. In this infant, transthoracic echocardiography with Doppler color flow mapping allowed direct visualization of a large right coronary artery to right ventricular fistula that was surgically corrected successfully.