Coronary arteriovenous fistula is an uncommon clinical entity. The right coronary artery is the most common site of origin, and the fistula commonly drains into the right-sided cardiac chambers. Very rarely it can arise from the left main coronary artery, and fistulas draining into the superior vena cavity are extremely rare. We report a 12-year-old asymptomatic boy with a large coronary arteriovenous fistula between the left main coronary artery and superior vena cava, with aneurysmal dilatation of the left main coronary artery. As the fistula was very large and to prevent its complications, it was planned to close the fistula percutaneously.