Herpes simplex encephalitis is known to cause intracranial hypertension and cerebral edema. When cerebral edema occurs, venous sinuses are compressed, resulting in congestion and thrombosis. An arteriovenous fistula may form as a result, particularly in conjunction with superior sagittal sinus thrombosis. In this report, the authors describe a patient with protein S and C deficiency who developed venous sinus thrombosis and dural arteriovenous fistula after experiencing herpes simplex encephalitis.