The 81-year-old male presented with progressive headache and was diagnosed as bilateral chronic subdural hemorrhage (SDH). He has history of hypertension, coronary artery disease and hyperlipidemia. Burr-hole craniostomy for removal of SDH was performed. However, deteriorated consciousness and seizure happened after removal of bilateral external ventricular drainage (EVD) on postoperative Day 3. The brain computed tomography (CT) scan showed bilateral tension pneumocephalus with significant mass effect and Mount Fuji sign. The patient underwent an emergency burr hole operation and the insertion of bilateral EVD. During the operation, the air bubbled out when the dura was opened. The patient’s consciousness subsequently improved and postoperative CT imaging showed considerable reduction in the pneumocephalus with relieved mass effect. Finally, the patient discharged with recovery neurological condition on the admission Day 11.