Anomalous origin of the coronary artery is rare. Various complications have been reported in patients with this anomaly undergoing heart valve surgery. We describe a case of aortic valve stenosis combined with an anomalous origin of the left coronary artery. An 84-year-old man with exertional dyspnea was referred for surgical treatment of severe aortic valve stenosis. Coronary angiography and computed tomography of the coronary artery revealed a coronary arterial anomaly : the left anterior descending coronary artery originated as a branch of the right coronary artery, and the left circumflex artery separately originated from the right coronary sinus and extended behind the aortic annulus. To prevent injury to the anomalous circumflex artery during surgery, the artery was separated from the fatty tissue around the aortic annulus and dissected free from the aortic wall before the performance of transverse aortotomy. The coronary artery exhibited a single orifice that was significantly enlarged. Whether antegrade infusion of the cardioplegic solution could be achieved was difficult to determine. To perform the retrograde infusion, the catheter tip was inserted directly into the coronary sinus from the epicardium because the orifice in the right atrium was lattice-like. Aortic valve replacement was successfully performed with supra-annular prosthesis insertion using a 19-mm Mosaic porcine valve (Medtronic, Minneapolis, MN, USA). The postoperative course was uneventful. When aortic valve replacement is performed for patients with an anomalous coronary artery, careful performance of operative procedures and postoperative observation are considered important for the prevention of specific perioperative complications, such as intraoperative coronary injury or postoperative myocardial ischemic events in patients with an anomalous left circumflex artery.