An 83-year-old female patient was managed in intensive care unit postoperatively with artificial ventilation and propofol-based sedation. On the second postoperative day, we tried to remove an endotracheal tube. Naloxone was administered to the patient for reversing the sedative effect of fentanyl infused intraoperatively. Her consciousness level was improved; however, subsequent administration of flumazenil induced hypnosis. Benzodiazepine-like partial agonistic effect of flumazenil might have enhanced residual hypnotic effect of propofol. Administration of flumazenil to the patient infused with propofol should be done cautiously for awakening the patient from anesthesia.