OBJECTIVES: This observational longitudinal study examines whether engagement in health behaviours (general health behaviours, sleep hygiene, comfort food snacking) mediate the link between self-compassion and mental health among emerging adults. DESIGN/METHOD: Participants were 332 emerging adults recruited from a large U.S. University (M RESULTS: T1 self-compassion was significantly associated with all T2 health behaviours except for comfort food snacking. T2 sleep hygiene behaviours mediated the relationship between T1 self-compassion and both T2 depression and T2 anxiety (bootstrapped 95% CIs [-.085, -.029] and [-.064, -.016], respectively), although the total effect of self-compassion on anxiety was no longer significant when accounting for T1 sleep hygiene and T1 anxiety. Overall T2 health behaviour engagement mediated the relationship between T1 self-compassion and T2 depression only (bootstrapped 95% CI [-.044, -.006]), although the mediation was non-significant after accounting for T1 overall health behaviour engagement and T1 depression. CONCLUSIONS: Findings suggest that individuals with higher self-compassion engage more in overall health behaviours and sleep hygiene practices, and that sleep hygiene and general engagement in health behaviours help to explain the link between self-compassion and mental health symptoms over time. These findings highlight the multiple positive downstream effects of fostering self-compassion and have important implications for mental health care providers utilizing self-compassion to support health behaviour engagement in order to promote mental health.