BACKGROUND: Chronic migraine (CM) is a significant neurological condition affecting a substantial portion of the global population. The economic burden of CM includes both direct healthcare costs and indirect costs resulting from productivity losses and intangible impacts on patients' quality of life. However, there is limited research that comprehensively evaluates all cost components associated with CM, highlighting the need for a systematic review. METHODS: We conducted a systematic literature search in databases including MEDLINE, Embase, and CINAHL to identify studies estimating the cost of illness of chronic migraines. The search was restricted to English language articles published from inception to October 2021, and only findings from Organisation for Economic Co-operation and Development (OECD) countries were included. Methodology features and key findings were extracted from the studies, and reported costs were converted to GBP for cross-country comparisons. RESULTS: Thirteen cost-of-illness studies on CM from various OECD countries were included in this review. The studies demonstrated substantial variations in monetary estimates, but consistently highlighted the considerable economic burden of CM. Direct costs, particularly hospitalisation and medication expenses, were identified as the highest contributors. However, indirect costs, such as productivity losses due to absenteeism and presenteeism, were often underexplored in the reviewed studies. Additionally, intangible costs related to emotional and social impacts on patients were largely overlooked. CONCLUSION: Chronic migraine imposes a significant economic burden on individuals, healthcare systems, and society. Policymakers and healthcare stakeholders should consider both direct and indirect cost components, as well as intangible costs, in developing targeted strategies for effective CM management and resource allocation. Further research focusing on comprehensive cost assessments and sensitivity analyses is needed to enhance the understanding of CM's economic implications and inform evidence-based healthcare policy decisions. Addressing these research gaps can alleviate the economic burden of CM and improve patient outcomes.