A male 3-year-old child was referred to our service due to increasing head size and mild headache. On physical examination, head circumference was 55 cm (bigger than 97th percentile), the child was conscious, alert and oriented to person, place, time and event, his pupils were isochoric, the light reflex was bilaterally positive, eye movements showed a slight palsy on the abduction of the left eye, and a partial vision loss on the left eye was detected. Gait was also impaired. MRI presented a cystic lesion in the suprasellar region suggesting arachnoid cyst, associated with hydrocephalus. An endoscopic ventricular approach was performed through a straight incision over Kocher’s point. The cyst was easily identified, coagulated with cautery and incised with endoscopic scissors. A ball-valve mechanism was well visualized. Prepontine cistern was also sharply opened and the whole cyst wall was coagulated. The patient was discharged on the second postoperative day showing a clinical improvement. Late head CT presented also a radiologic improvement.