Pneumothorax is a rare but potentially serious complication that can occur during laparoscopic surgery. We describe a case of a spontaneous massive right-sided pneumothorax that occurred during laparoscopic cholecystectomy, presumably because of escape of intraperitoneal carbon dioxide under pressure into the pleural cavity through a congenital defect in the diaphragm. During the procedure, arterial oxygen saturation decreased and clinical examination revealed signs of a right-sided pneumothorax. This was confirmed on chest x-ray in the immediate postoperative period. Since the patient was clinically stable without any signs of respiratory distress, a conservative approach was adopted. The patient remained on close clinical observation and continuous monitoring of arterial hemoglobin oxygen saturation by pulse oximetry and repeat chest x-rays and had an uneventful recovery with complete resolution of the pneumothorax 3 hours after surgery and without the need for thoracic aspiration or tube thoracostomy.