Endoscopic third ventriculostomy (ETV) is an effective and rather safe treatment for noncommunicating hydrocephalus secondary to aqueductal stenosis and other obstructive pathologies. It has become a popular alternative to ventricular shunts for noncommunicating hydrocephalus. Although it is a safe procedure, several complications related to this procedure have been reported in the literature. We report a rare case of a large chronic subdural hematoma (ChSDH) after ETV in a patient with aqueductal stenosis. A 42-year-old female patient presented with acute symptoms of obstructive hydrocephalus, headaches and blurring of consciousness. A computerized tomogram (CT) of the patient's brain revealed marked triventricular supratentorial hydrocephalus and an external ventricular drainage (EVD) was performed first. After this procedure, magnetic resonance imaging (MRI) demonstrated hydrocephalus secondary to aqueductal stenosis. ETV was performed and the EVD removed uneventfully. The patient was discharged home after a few days without any complications. She then presented with headaches 4 weeks following ETV. A CT demonstrated chronic subdural hematoma on the contralateral side. This was treated with burr-hole evacuation. Postoperatively, her headaches improved. During the follow-up period, she remains symptom-free and has radiographic evidence of a patent ventriculostomy. This case confirms chronic subdural hematoma formation is a possible complication following endoscopic third ventriculostomy.