Traumatic intracranial aneurysms are rare, and their occurrences can only be assumed in the presence of major head injury, unusual location and rather unique radiological findings. We describe one patient having giant pseudoaneurysm arising at distal middle cerebral artery. A 22-year-old woman presented with sudden mental deterioration. She had suffered minor head injury 2 months ago, and complained headache since then. Brain computed tomography and angiography revealed thick subarachnoid hemorrhage, huge intraparenchymal hematoma and aneurysmal dilatation at the distal middle cerebral artery. Surgical trapping and excision of the ruptured aneurysm were conducted. Histopathological examination confirmed a pseudoaneurysm and she recovered gradually thereafter. Although there had been no definite evidence of recent major head injury, peripheral location of the aneurysm, histologically proven pseudoaneurysm and clinical deterioration following 2 months of minor head injury all made us believe that this aneurysm might be caused by trauma.