The in vivo sedative property of the total aqueous extract of the aerial portion of Vervain hastata (Verbenaceae) (TAEV) was studied in male rats to establish its scientific basis in herbal medicine. The investigation was conducted using electroencephalogram (EEG) analysis, and the barbituric-hypnosis test. The results showed that TAEV potentiated the pentobarbital-induced hypnosis significantly by reducing sleep latency and increased sleeping time in a dose-dependent manner that was reversed by flumazenil. The EEG data demonstrated that extract administration augmented total sleep time, rapid eye movement (REM) sleep and non-REM sleep at the expense of wakefulness. The study's results clearly showed the scientific validity for the use of this plant as a sedative and possibly as a nerve tonic substance.