Hydatidosis is an endemic affection in Tunisia. Cerebral echinococcosis is a relatively rare entity accounting for only 1-2% of all hydatid cysts in humans. Extradural hydatid cyst of the posterior fossa is a very uncommon site for the disease. We report the case of a four-year-old child admitted for high intracranial pressure. Brain CT scan showed an extradural posterior fossa cyst without enhancement after contrast medium injection. Operative finding revealed a hydatid cyst. The histological examination of the tissue sample confirmed the diagnosis. The patient was given albendazole post operatively. She feels well six months later.