Pneumocephalus is defined as the presence of air in the intracranial cavity. In most cases, its evolution is asymptomatic and benign. Pneumocephalus post-surgery is a frequent complication of cranial surgery. We herein report delayed tension pneumocephalus after craniotomy for pituitary macroadenoma. A 73-year-old man with recurrent pituitary macroadenoma underwent subtotal resection via subfrontal approach. The postoperative course was uneventful and the patients regained his normal daily living activities. Two months after the surgery the patients developed decreased level of consciousness and was diagnosed to suffer from tension pneumocephalus. Another craniotomy was performed and the dural defect at the base was repair with secondary graft and bone wax. The patient improved neurologically and had no pneumocephalus. The follow-up revealed good condition and outcome. In conclusion, tension pneumocephalus can occur at any time after craniotomy and post-surgical deterioration after resection of a giant pituitary tumor should be immediately assessed. There is not enough evidence to correlated tumor size with rates of pneumocephalus in this particular report, but further cases may need to be studied to come to a conclusion.