Arachnoid collapse is a previously unreported complication of endoscopic choroid plexus coagulation (ECPC) treatment of hydranencephaly and is demonstrated in this case report. The variable anatomy found in hydranencephaly supports the use of ECPC as the preferred treatment option. However, the same anatomical anomalies predispose the procedure to this unique complication. A brief literature review of hydranencephaly has also been performed and is reported through the discussion. Neurosurgeons must be aware of this very dangerous complication and a discussion of preventative measures are made. The use of ECPC and the clinical expectations of treating patients with hydranencephaly is also discussed.