Objective <p>Insomnia and hypersomnia are sleep conditions associated with significant costs to the healthcare system and society. This study aimed to review the cost-effectiveness evidence of interventions for insomnia and hypersomnia, including psychotherapy, pharmacotherapy, and complementary and alternative medicine (CAM), across the age spectrum.</p> Methods <p>A systematic search (from inception to 18th February 2025) was conducted in electronic databases (Medline, PsycINFO, CINAHL, Econlit and Embase) and Health Technology Assessment websites. Full economic evaluations and return-on-investment analyses were included if they focused on treatments targeting insomnia or hypersomnia in people aged ≥12 years. The Drummond checklist was used to evaluate the quality of eligible studies. Narrative synthesis was applied to extract study characteristics and economic evaluation outcomes.</p> Results <p>Twenty-eight studies met the pre-defined criteria, including 26 for adults and older adults with insomnia, two for adolescents with insomnia, and no studies were found for hypersomnia treatment. Cognitive behavioural therapy for insomnia (CBT-I) and pharmacotherapy were likely to be cost-effective interventions for insomnia compared to inactive controls. Digital CBT-I was found to generate healthcare and societal cost savings when compared to face-to-face CBT-I or pharmacotherapy. The cost-effectiveness of CAM interventions is under-researched and remains unclear.</p> Conclusion <p>Among insomnia interventions, CBT-I has the strongest cost-effectiveness credentials. Future studies should focus on hypersomnia, adolescent insomnia, and comorbid insomnia and related conditions.</p> PROSPERO Registration Number <p>CRD42022343067.</p>