Intracranial aneurysm rupture usually manifests with subarachnoid hemorrhage, often combined with intracerebral hemorrhage with intraventricular hemorrhage extension. In rare cases, however, these aneurysms present only as subdural hematomas. Recently, we treated a 48-years-old female patient who presented only with subdural hematoma. Interestingly, she did not have a history of trauma. Computed tomography angiography and digital subtraction angiography revealed a 5 × 3 mm sized aneurysm at the A3-A4 junction of the left anterior cerebral artery. On admission, emergency operation (clipping and hematoma evacuation) was performed to protect against re-bleeding. Along with postoperative intensive care, the patient returned to normal daily life with only a mild headache. Given that patients may present with atraumatic acute subdural hematoma, the clinician must bear in mind the possibility of intracranial vascular pathology and obtain angiographic scans to evaluate for any underlying conditions to prevent patient deaths.