Hiccups are common reflexes and many treatment methods have been reported. Chlorpromazine is a known treatment option for hiccups, but its efficacy under general anesthesia remains unclear. We report the case of a patient with vagal schwannoma who developed hiccups while under general anesthesia. Muscle relaxants were not used because the patient was under neuromonitoring. The depth of anesthesia was deepened; however, the hiccups did not disappear. The hiccups were relieved by intravenous chlorpromazine administration (total; 5 mg), which allowed for surgery under neuromonitoring. This case indicates that chlorpromazine may be effective to treat hiccups under general anesthesia.