Hydatid disease is a parasitic infection affecting the brain in about 2% of the cases. Brain involvement is most commonly observed in children. Here, we report a 13-year-old male patient who presented with headache, nausea, and vomiting. Before cranial computed tomography (CT) was performed, the patient had generalized epileptic seizures. He was disoriented, and had anisocoria with dilatation of the right pupilla. CT showed a cystic lesion of 10-cm diameter in the right temporoparietal region that had caused a shift of the midline structures to the contralateral side; an urgent operation was performed as there were signs of midbrain herniation.