Parasagittal meningioma often presents as peritumoral brain edema (PTBE). The risk of edema increases when the tumor occludes the superior sagittal sinus (SSS). Although PTBE may be expected based on the patient’s symptoms or radiologic findings, extensive brain swelling and extracranial herniation during elective surgery are rare. Herniation during surgery could lead to irreversible neurological damage and even brain rupture. We report a case of a failed routine craniotomy for a parasagittal meningioma with complete occlusion of the posterior third of the SSS in a 30-year-old male patient. The patient developed extensive brain swelling and extracranial herniation during surgery.