Coronary artery fistulae are uncommon but may be haemodynamically significant, being an incidental finding in 0.1–0.2% of coronary angiograms. Even rarer is the association between fistulae and non-atherosclerotic coronary artery aneurysms. They most frequently originate in the right coronary artery, and the right cardiac chambers are the most common draining chambers. Most children are asymptomatic, whereas those older than 20 years may present with signs of congestive heart failure, infective endocarditis, myocardial ischaemia, or aneurysm rupture. Management is either surgical or via percutaneous means. We report the case of a 5-year-old child referred for assessment of an asymptomatic cardiac murmur. The echocardiographic evaluation showed an enlarged right atrium, a fenestrated atrial septal defect, and a giant right coronary artery aneurysm with a fistulous tract that appeared to drain directly into the right atrium. Computed angiocardiac tomography and cardiac catherisation confirmed the presence of a large right coronary fistula originating from the right coronary aneurysm draining into the right atrium. The patient underwent surgical ligation of the fistula and the post-operative course has been uneventful. He is currently on double antiaggregation therapy.