Superficial temporal artery (STA) to middle cerebral artery (MCA) anastomosis may have inadequate effects in patients with internal carotid artery (ICA) occlusion and severe stenosis of the ipsilateral external carotid artery (ECA), because poor blood flow in the STA leads to insufficient flow to the MCA. In these patients, dilation of the stenotic ECA is required to improve the blood flow in the STA before STA-MCA anastomosis. A 71-year-old man presented with left hemiparesis and dysarthria. Magnetic resonance imaging revealed an old watershed infarction in the right cerebral hemisphere. Right carotid angiography showed right ICA occlusion and severe ipsilateral ECA stenosis. Single photon emission computed tomography (SPECT) demonstrated severe hemodynamic insufficiency in the right MCA territory. Instead of endarterectomy of the ECA, angioplasty and stenting (CAS) for ECA was performed to ensure adequate blood flow in the STA, due to the history of myocardial infarction and bifurcation of the common carotid artery at a high level (C2 level). Then STA-MCA anastomosis was performed 1 month later. Postoperative SPECT demonstrated marked improvement of hemodynamic insufficiency in the right MCA territory. After treatment, the patient had no ischemic events. This case suggests external CAS together with STA-MCA anastomosis is a good therapeutic option for a patient with symptomatic ICA occlusion and severe stenosis of the ipsilateral ECA if external CEA is difficult to perform.