True posterior communicating artery aneurysms are extremely rare with incidence ranges from 0.1% to 2.8% of all aneurysms. Cerebral aneurysm formation has been reported as a complication of artery occlusion by flow alteration. We present a 69 years old male patient presenting with subarachnoid hemorrhage with diagnosis of true right posterior communicating artery aneurysm. He had a left subclavian artery occlusion with flow theft from the right vertebral artery to the left vertebral artery. The patient underwent endovascular treatment with angioplasty and stent placement on the left subclavian artery and aneurysm occlusion result. We discuss the reestablishment of cerebral blood flow as a treatment for this aneurysm.