Congenital atresia of the left main coronary artery ostium is a rare lesion, particularly when found in association with supravalvar aortic stenosis. This report describes the preoperative evaluation and surgical management of this lesion found in conjunction with a quadricuspid aortic valve in a 5-year-old child. Patch aortoplasty and left internal thoracic artery to left anterior descending coronary artery bypass were performed to correct this lesion.