Tension pneumoventricle is an uncommon but potentially life-threatening complication of ventriculoperitoneal (VP) shunt placement. It results from the accumulation of pressurized intraventricular air, producing mass effect and neurological deterioration. Its occurrence following VP shunt surgery is exceedingly rare. A 24-year-old man with obstructive hydrocephalus due to aqueductal stenosis underwent right-sided VP shunt placement with symptomatic improvement. Two weeks later, he developed cerebrospinal fluid rhinorrhea. Computed tomography revealed significant intraventricular air with ventricular distortion consistent with tension pneumoventricle. Magnetic resonance cisternography demonstrated a left frontal encephalocele with a fistulous tract extending from the frontal sinus into the frontal horn of the lateral ventricle. The patient underwent bifrontal craniotomy, excision of the encephalocele, frontal sinus cranialization, and multilayered dural repair using a vascularized pericranial graft. Postoperative recovery was uneventful, and follow-up imaging confirmed complete resolution. VP shunt–induced intracranial hypotension may unmask occult skull base defects, facilitating air entry through a pressure-gradient mechanism. Early diagnosis and definitive surgical repair are essential to prevent recurrence and infectious complications.