This study evaluated the effects of a rosmarinic acid– and epigallocatechin gallate–enriched extract mixture (RE-GTE) on insomnia and sleep–wake disturbances induced by excessive caffeine intake or serotonin depletion using p -chlorophenylalanine (PCPA) in mice. RE-GTE was administered in both caffeine- and PCPA-induced insomnia models, and sleep-related behaviors were assessed using pentobarbital-induced sleep tests and behavioral analyses of anxiety-related and locomotor parameters. In addition, sleep-related neurotransmitters and receptor expression were examined using molecular and biochemical approaches. In the caffeine-induced insomnia model, RE-GTE supplementation significantly attenuated caffeine-induced dopaminergic hyperactivity, increased gamma-aminobutyric acid (GABA) levels, and improved anxiety-related and selected locomotor behavioral parameters. RE-GTE also upregulated GABA _A receptor expression while reducing adenosine A1 and A2A receptor expression, accompanied by increased sleep duration. In the PCPA-induced insomnia model, RE-GTE increased hypothalamic serotonin and melatonin levels, reduced stress-related hormones including adrenocorticotropic hormone and corticosterone, increased serotonin receptor expression, and reduced overexpression of the orexin 2 receptor, indicating selective modulation of serotonergic and stress-related markers. Across both models, high-dose RE-GTE (40 mg/kg) increased sleep duration toward normal levels. Collectively, these findings indicate that RE-GTE ameliorates insomnia-related behavioral and neurochemical disturbances and that this improvement is accompanied by selective changes in adenosinergic, GABAergic, and serotonergic markers. These pathway-level associations support further investigation of RE-GTE as a promising natural candidate for the management of sleep disturbances.