A rare case of delayed lateral rectus palsy in a patient following resection of a pineal lesion in the sitting position is presented. Postoperative pneumocephalus is common following craniospinal surgical intervention in the sitting position. The sixth cranial nerve is frequently injured because of its prolonged intracranial course. A 13-year-old girl was evaluated for unremitting headaches. No focal deficits were demonstrated on neurological examination. Magnetic resonance imaging revealed a cystlike pineal region mass with peripheral enhancement following intravenous contrast administration. A supracerebellar infratentorial craniotomy was performed in the sitting position, and complete resection of the lesion was achieved. Her postoperative course was complicated by sixth nerve palsy on the third postoperative day. Her symptoms improved with conservative management. The occurrence of sixth cranial nerve palsy secondary to pneumocephalus is a rare entity. Even rarer is the report of this anomaly following craniotomy in the sitting position. This patient's symptoms manifested in a delayed fashion. Although uncommon, this complication should be considered in patients undergoing cranial or spinal surgical interventions in this position.