A 71-year-old female with esophagohiatal hernia underwent a laparoscopic Nissen's fundoplication under general anesthesia. During the operation a Savary-Gilliard bougie was temporarily inserted to the esophagus to prevent esophagostenosis. After the emergence from anesthesia, the patient complained of severe back pain and developed tachypnea and a low SpO2 associated with an enlargement of mediastinal shadow on the chest X-ray, suggesting mediastinal perforation. Examination by endoscopy and thoracotomy revealed a pyriform sinus perforation reaching down to the mediastinum. This case demonstrates the possibility of accidental perforation by various devices inserted blindly to esophagus, especially during general anesthesia, and the importance of close observation of patients after the emergence from anesthesia.