A 57-year-old man presented with sudden-onset consciousness disturbance. He had a 10-year history of a subarachnoid hemorrhage(SAH)caused by a ruptured aneurysm in the right middle cerebral artery, and had undergone aneurysmal clipping. He could perform all his daily life activities independently. Computed tomography showed diffuse SAH with intraventricular hemorrhage. Digital subtraction angiography(DSA)demonstrated mild fusiform dilatation of the left A2 portion of the left anterior cerebral artery(ACA)and the terminal portion of the left internal carotid artery with no sign of right middle cerebral artery(MCA)aneurysm recurrence. We could not identify the bleeding lesion at that time; therefore, conservative treatment was selected in the acute phase. Fourteen days later, repeated DSA showed fusiform dilatation of the left A2 portion leading to a diagnosis of ACA dissection. We initially performed superficial temporal artery(STA)-ACA anastomosis and secondary internal trapping with detachable coils in the operating room. Postoperative DSA revealed complete obliteration of the dissection and parent artery. Endovascular treatment with STA-ACA bypass is a safe and effective alternative for the treatment of ACA dissection.