A 69-year-old man was referred to our hospital because of a right upper mediastinal mass observed on chest roentgenogram. Computed tomography showed a dissecting aneurysm of the right subclavian artery and dissection of the ascending aorta. Furthermore, the ascending aorta was dilated. We subsequently reconstructed the right subclavian artery with a bypass graft and replaced the ascending aorta. Two-thirds of the aortic arch was placed in deep hypothermic circulatory arrest with retrograde cerebral perfusion. His postoperative course was uneventful with no neurological complications. While subclavian artery aneurysms are relatively rare in comparison to other peripheral artery aneurysms, subclavian artery aneurysms with aortic dissections are even rarer. The most important concerns during subclavian artery aneurysm repair are the method of surgical approach and the maintenance of sufficient cerebral flow. We suggested that deep hypothermic circulatory arrest with retrograde cerebral perfusion might prove useful in cases involving an intramural thrombus adherent to cerebral vessels. Therefore, patients with subclavian artery aneurysms must undergo extensive preoperative evaluation.