A 67-year-old woman encountered a traffic accident and had chest computed tomography（CT） examination. It revealed a 24 mm Kommerell’s diverticulum associated with a right-sided aortic arch and a 15 mm saccular aneurysm of an aberrant left subclavian artery. We performed intra-aneurysmal coil embolization for the left subclavian artery aneurysm after a balloon occlusion test of the left subclavian artery. The postoperative course was uneventful.