A 43-year-old male presented with headache localized in the right forehead. Computed tomography and magnetic resonance imaging demonstrated a cystic mass in the frontal sinus, with a huge extension into the anterior cranial fossa. The mass was removed by transcranial surgery. The cyst contained pus. Histological examination of the cyst wall revealed mucocele (pyocele). Pyocele with huge intracranial extension is rare and requires combined neurosurgery and otolaryngology for optimum treatment.