A 37-year-old female patient, 57 kg and 160 cm, underwent laparoscopic appendectomy. In the recovery room, fentanyl 100 mcg was intravenously administered for pain control. Three minutes after the administration, the patient developed intense and uncontrolled myoclonus, lower limb rigidity, agitation, aphasia, and periocular and neck swelling. The myoclonus and rigidity were suspected to be due to the opioid administration, and thus, naloxone was administered, but the symptoms were not improved. The patient's symptoms continued until the patient received administration of physostigmine. The patient was discharged 3 days later, following resolution of the symptoms. We report a case of central anticholinergic syndrome that developed after general anesthesia owing to the interaction of opioid at an analgesic dose for postoperative pain control with another anesthetic.