BACKGROUND: Icariin (ICA) is a bioactive monomer derived from Epimedium. The aim of this study was to evaluate the sedative-hypnotic effect of ICA and to investigate its mechanism. METHODS: C57BL/6J mice were injected intraperitoneally with a suspension of PCPA (300 mg/kg) for two consecutive days to establish an insomnia model. Three different doses of ICA (50, 100, and 200 mg/kg/day) were given to C57BL/6J mice for 7 days. The weight changes were measured, and open field tests and pentobarbital sodium-induced sleep tests were conducted. The levels of 5-hydroxytryptamine (5-HT) and γ-Aminobutyric acid (GABA) in the cerebral cortex, hippocampus, and hypothalamus were measured using enzyme-linked immunosorbent assay (ELISA) kits. The expression of GABAAα1 and GABAAγ2 was measured by Western blot (WB) and Real-time PCR (qPCR). RESULTS: Notably, ICA increased body weight, shortened sleep latency, and prolonged sleep duration in insomniac mice. Furthermore, ICA effectively increased the contentl of GABA and 5-HT in the brain tissue of insomnia mice. Moreover, ICA significantly increased the expression of GABAAα1 and GABAAγ2 in insomnia mice. CONCLUSION: ICA showed significant sedative-hypnotic effects in insomnia mice through the GABAergic system pathway.