A coronary artery aneurysm is an uncommon anomalous disease, defined as a coronary dilatation that exceeds the diameter of normal adjacent segments or the diameter of the patient's largest coronary vessel by 1.5 times. They are usually asymptomatic and diagnosed incidentally by coronary angiography. However, they may also cause angina, myocardial infarction, sudden cardiac death due to thrombosis, embolization or rupture. This report describes one case of a huge coronary artery aneurysm with total occlusion of the left anterior descending artery, resulting in a non ST elevation myocardial infarction, which was treated with bypass graft surgery and excision of the coronary artery aneurysm.