An 18 month-old boy underwent endoscopic foreign body removal under anesthesia on an outpatient basis and the operation took approximately 5 minutes. Stridor developed in both lung fields 6 hours after emergence from anesthesia, and severe croup developed, with cyanosis of the lips and aggravated stridor 20 hours after the end of the procedure. The croup resolved with oxygen therapy, intravenous dexamethasone, and epinephrine nebulization therapy. In this report, we suggest that thorough investigations of the patient's past history, including history of any airway problems, and careful monitoring after emergence from anesthesia be done in order to decide the proper discharge time of the patient. Further, proper prophylaxis following risk stratification is important, especially in patients at high risk of postoperative airway obstruction.