A 63-year-old man presented with sudden severe headache. Computed tomography (CT) demonstrated subarachnoid hemorrhage. Cerebral angiography demonstrated an aneurysm of the anterior communicating artery. Left frontotemporal craniotomy and neck clipping of the aneurysm via the pterional approach were performed. CT obtained 18 hours after surgery revealed cerebellar hemorrhage, and magnetic resonance (MR) imaging 17 days postoperatively demonstrated that the hemorrhage was located within the folia. Neurological examination after surgery revealed slight dysarthria after drainage of cerebrospinal fluid (CSF) but no other neurological deficits. Follow-up CT and MR imaging showed characteristic findings of postoperative cerebellar hemorrhage clearly different from those of hypertension. The cerebellar hemorrhage was probably secondary to overdrainage of CSF. He was discharged without deficits.