Congenital coronary arteriovenous fistula is a rare condition which is an abnormal communication of the coronary artery with the right ventricle, right atrium, left atrium or left ventricle. Coronary artery aneurysm is an uncommon disease which is defined as coronary dilatation which exceeds the diameter of normal adjacent segments or the diameter of the patient's largest coronary vessel by 1.5 times. In young ages, symptoms are unusual, but significant symptoms and complications such as congestive heart failure, subacute bacterial endocarditis, coronary steal syndrome, aneurysm formation, rupture, and pulmonary hypertension may appear among the older age group. We report a case of giant aneurysm of a congenital coronary arteriovenous fistula between left co-ronary artery and right ventricular outflow tract with significant left to right shunt confirmed in a 84-year old female with a brief review of literature.