Coronary artery aneurysm, especially left main coronary artery (LMCA) aneurysm is a rare phenomenon. The disease may be congenital or acquired. The most common cause of coronary artery aneurysm is atherosclerosis. We presented a man with a large LMCA aneurysm presenting with unstable angina, transient ischemic attack, ventricular tachycardia and paroxysmal atrial fibrillation.