A 75-year-old man who had undergone left upper lobectomy of the lung exhibited fever and insomnia on postoperative day (POD) 1 and muscle rigidity, autonomic instability, and somnolence on POD2 after epidural administration of droperidol and withdrawal of oral etizolam. He had not been known to have any neuromuscular diseases or psychiatric diseases, with the exception of anxiety disorder. Brain computed tomography did not show cerebrovascular disorders. Consultation with a neurologist led to a suspicion of neuroleptic malignant syndrome (NMS). Epidural droperidol was stopped and administration of dantrolene was initiated. These measures, in addition to supportive care, only partially ameliorated the symptoms of the patient, and consciousness disturbance developed; the patient finally became comatose on POD3. However, intravenous diazepam (10 mg) improved his symptoms abruptly. Subsequently, oral administration of lorazepam (1 mg/day) was started, and his symptoms disappeared within 2 days (POD5). Although NMS-like symptoms are rarely seen in clinical practice, some factors may induce it during the perioperative period, such as the administration of dopamine antagonists and the cessation of benzodiazepines. Intravenous diazepam is an effective treatment in cases with suspected gamma-aminobutyric acid (GABA) hypoactivity at the GABA(A) receptor induced by the cessation of benzodiazepines.