Background: Coriandrum sativum L. has been recommended for relief of insomnia in Iranian traditional medicine. However, no pharmacological studies have yet evaluated its sedative effects. The aim of this study was to determine if extracts and essential oil of coriander seeds have sedative-hypnotic activity. Methods: The aqueous or hydro-alcoholic extracts or essential oil of coriander seeds (100, 200, 400 and 600 mg/kg) were intraperitoneally administered to male albino mice, 30 minutes before pentobarbital injection (40 mg/kg). Latency to sleep and sleep duration were recorded. Results: Aqueous extract prolonged pentobarbital-induced sleeping time at 200, 400 and 600 mg/kg. Hydro-alcoholic extract at doses of 400 and 600 mg/kg increased pentobarbital-induced sleeping time compared to saline-treated group. The essential oil increased pentobarbital-induced sleeping time only at 600 mg/kg. Conclusion: The extracts and essential oil of coriander seeds possess sedative-hypnotic activity. However, it is strongly suggested that the major active component(s) responsible for the hypnotic effect is mainly present in the aqueous extract.