The present study was performed to investigate the effects of valerian extract on the sleep-wake cycle using sleep-disturbed model rats. A significant shortening in sleep latency was observed with valerian extract at doses of 1000 and 3000 mg/kg. On the other hand, valerian extract had no significant effects on total times of wakefulness, non-rapid eye movement (non-REM) sleep, or REM sleep, even at a dose of 3000 mg/kg. Valerian extract at doses of 1000 and 3000 mg/kg showed a significant increase in the delta activity during non-REM sleep. In conclusion, valerian extract may be useful as an herbal medicine having not only sleep-inducing effects but also sleep quality-enhancement effects.