Percutaneous nephrolithotomy (PCNL) has largely replaced open surgical intervention for the management of renal pelvis calculi as it reduces patient morbidity and shortens hospital stay. However, major complications such as hydrothorax or pneumothorax can be encountered uncommonly. A 64-year-old, 48 kg, female patient underwent PCNL under general anesthesia. The preoperative chest X-ray showed normal findings. Elevated airway pressure was noted and then breathing sounds were not audible on the right lung field during the procedure. A chest X-ray and chest computerized tomographic scan, taken immediately after the operation, showed massive hydrothorax and total collapse in the right lung. After drainage of the pleural effusion via chest tube, the patient recovered completely. Anesthesiologists should be aware that hydrothorax can occur during the PCNL procedure and must be prepared to intervene quickly.