Coronary artery aneurysms are rare, especially in the left main coronary artery. Coronary artery aneurysms may rupture or cause myocardial infarction. There are only a few reports of coronary artery aneurysms of the left main coronary artery treated surgically. We report a case in which an arterial graft from the internal iliac (hypogastric) artery was used for the reconstruction of a congenital coronary artery aneurysm of the left main coronary artery. After a follow-up of 5 years, the patient is well and in good condition.