Background: Hydrocephalus in infancy is usually treated with a ventriculo-peritoneal (VP) shunt, however, endoscopic third ventriculostomy (ETV) is a recent surgical option of treatment which if succeeded, avoids shunt insertion complications. Aim of the work: to analyze the OUTCOME of ETV as a treatment for hydrocephalus in infants aged less than 1 year. Patients and methods: An analytical prospective study conducted on 40 infants suffering from obstructive hydrocephalus (28 infants with congenital aqueductal stenosis and 12 infants with post meningitic hydrocephalus) in infants younger than one year of age treated via ETV approach in Al Azhar university hospitals in the period September 2017 to September 2020. Follow up of patients done clinically and radiologically over 6 months. Results: The clinical success rate in our study was achieved in 22 cases (55%) while failure was encountered in the remaining 18 cases (45%) When comparing successful and failed cases, no significant difference was detected between the two groups regarding patient age (p = 0.095). Conversely, it was evident that the prevalence of post-meningitic stenosis was significantly more common in the failed group (44.44% vs. 18.18% in the successful group -p < 0.001). Success rates were significantly different in infants with aqueductal stenosis 18case (81.82%). Conclusion:ETV can be the definitive treatment for obstructive hydrocephalus with different etiologies in infants less than one year of age. Success rate of ETV depends not only on the age but mainly on the cause of hydrocephalus, preoperative MRI findings and surgeon endoscopic experience.