Percutaneous nephrolithotomy (PCNL) effectively treats large stones or stones in the lower renal poles. The complication fate for the subcostal approach is lower than for the supracostal approach, and complications generally can be avoided by using a working (Amplatz) sheath and by inserting a large nephrostomy tube after the procedure. We present the case of a patient who developed a left pleural effusion during a subcostal PCNL for a left renal stone. A working sheath had been used, and a nephrostomy tube had been inserted for drainage and tract tamponade after the procedure. Our report is intended to alert colleagues that even though pleural effusion is a rare complication of subcostal PCNL, it could cause intraoperative high airway pressure and hypoxemia.