Purpose: Tension pneumocephalus (TP) represents a rare pathology characterized by constant accumulation of air in the intracranial space, being associated with increased risk of herniation, neurologic deterioration and death. Regarding neurosurgical trauma cases, TP is majorly encountered after chronic subdural hematoma evacuation. In this case report, we present a rare case of fatal postoperative TP encountered after craniotomy for evacuation of acute subdural hematoma (aSDH).Case Presentation: An 83-year old gentleman was presented to the emergency department of our hospital with impaired level of consciousness. Initial examination revealed Glascow Coma Scale (GCS) 3/15, with pupils of 3 mm bilaterally and impaired pupillary light reflex. CT scan demonstrated a large left aSDH, with significant pressure phenomena and midline shift. Patient was subjected to an uneventful evacuation of hematoma via craniotomy and a closed subgaleal drain to gravity was placed. The following day and immediately after his transfer to the CT scanner, he presented with rapid neurologic deterioration with acute onset anisocoria and finally mydriasis with fixed and dilated pupils. Postoperative CT scan showed massive TP, and the patient was transferred to the operating room for urgent left decompressive craniectomy, with no intraoperative signs of entrapped air intracranially. Finally, he remained in severe clinical status, passing away on the eighth postoperative day.Conclusion: TP represents a rare but severe neurosurgical emergency that may be also encountered after craniotomy in the acute trauma setting. Involved practitioners should be aware of this potentially fatal complication, so that early detection and proper management are conducted.