Résumé : Abstract Growing aging populations pose a threat to global health because of the social and psychological challenges they experience. To mitigate this, many countries promote hobby engagement to support and improve mental health. Yet, it remains unclear whether there is consistency in benefits across different national settings. We harmonized measures of hobby engagement and multiple aspects of mental wellbeing across 16 nations represented in five longitudinal studies ( N  = 93,263). Prevalence of hobby engagement varied substantially across countries, from 51.0% of Spanish respondents to 96.0% of Danish respondents. Fixed effects models and multinational meta-analyses were applied to compare the longitudinal associations between hobbies and mental wellbeing. Independent of confounders, having a hobby was associated with fewer depressive symptoms (pooled coefficient = −0.10; 95% confidence intervals (CI) = −0.13, −0.07), and higher levels of self-reported health (pooled coefficient = 0.06; 95% CI = 0.03, 0.08), happiness (pooled coefficient = 0.09; 95% CI = 0.06, 0.13) and life satisfaction (pooled coefficient = 0.10; 95% CI = 0.08, 0.12). Further analyses suggested a temporal relationship. The strength of these associations, and prevalence of hobby engagement, were correlated with macrolevel factors such as life expectancy and national happiness levels but overall, little variance in findings was explained by country-level factors (<9%). Given the relative universality of findings, ensuring equality in hobby engagement within and between countries should be a priority for promoting healthy aging.