Spontaneous acute arterial subdural hematoma (SDH) is a rare entity caused by hemorrhage from a cortical perisylvian artery without a known precipitant.A 53-year-old man presented with a 2-day history of acute-onset headache and dysphasia. He had a generalized seizure on arrival to hospital and no history of trauma. A computed tomography demonstrated an acute left-sided SDH. A computed tomography angiogram and a digital subtraction angiogram demonstrated active contrast extravasation into the SDH. A craniotomy was performed to evacuate the hematoma; the bleeding perisylvian artery was visualized and coagulated.We report a rare case of acute SDH and present a review of the literature. The etiology, investigation, and management of this rare neurosurgical emergency are discussed.