Background Hydrocephalus in patients with neurofibromatosis (NF) type 1 is usually obstructive and may arise secondary to tumoral or nontumoral causes. Treatment of hydrocephalus in these patients is often challenging owing to combined pathologies and unique anatomic changes. The use of endoscopic third ventriculostomy (ETV) as treatment has rarely been described in this group. We aimed to characterize indications, considerations, and outcome of ETV in patients with NF 1 gathered in a multicenter international cohort. Methods Five centers participated in this retrospective study. Following institutional review board approval, data and images were collected. Patients of all ages with NF 1 who underwent ETV for treatment of obstructive hydrocephalus were included. Patients who had no postoperative radiologic or clinical follow-up were excluded. ETV failure was defined as recurrent clinical or radiologic signs of hydrocephalus. Results The study included 42 patients. Common etiologies for hydrocephalus were aqueductal/tectal tumor (31%), aqueductal web (26%), and aqueductal stenosis owing to NF-related changes (14%). Ten patients had a preoperative diagnosis of optic pathway glioma. ETV failures were identified in 6 patients within 1 month, in 3 patients within 9 months, and in 1 patient within 4 years. ETV was successful in 32 patients (76%) with a mean follow up of 59.4 months ± 50.9 (range, 4 months to 15 years). Conclusions ETV is a safe treatment for selected patients with NF 1 and obstructive hydrocephalus. Individual anatomic and pathologic aspects should be taken into consideration. © 2017 Elsevier Inc.