Objective: This study examined the mediating effects of lifelong learning on the association between self-rated health and educational attainment among a nationally representative sample of US residents aged 50 years and older. Setting: Socioeconomic disparities in health are a major public health concern in economically developed nations where improving socioeconomic status (e.g. formal educational attainment) at the population level is challenging. In the light of population ageing, alternative approaches to improve health through malleable factors are urgently needed. Recent research suggests that participation in organised learning activities -- lifelong learning -- could attenuate the lack of formal educational attainment on health. Methods: Data come from the 2012 wave of the US Health and Retirement Study. Structural equation models with bootstrapping were used to estimate the mediation effect of lifelong learning activity in the relationship between self-rated health and formal educational attainment. Results: Approximately 3%-5% of the effect of formal education on self-rated health was mediated by lifelong learning activity. Findings from this study support the notion that ongoing participation in organised learning activities is beneficial for health in later life. Conclusion: Lifelong learning reflects a promising autonomous and sustainable strategy to improve health in later life. Future public health and education policy as well as education institutions should consider providing more learning opportunities for older populations.