Emerging evidence indicates self-compassion can be beneficial for medical populations and for medical adherence; yet, research to date has not fully examined the reasons for this association. This study examined the association of dispositional selfcompassion to adherence across five medical samples and tested the extent to which perceived stress accounted for this association. Five medical samples (total N = 709), including fibromyalgia, chronic fatigue syndrome, and cancer patients, recruited from various sources, completed online surveys. Self-compassion was positively associated with adherence in all five samples. A meta-analysis of the associations revealed a small average effect size (average r = .22, [0.15, 0.29]) of self-compassion and adherence and non-significant heterogeneity among the effects (Q (4) = 3.15, p = .532). A meta-analysis of the kappa 2 values from the indirect effects of self-compassion on adherence revealed that, on average, 11% of the variance in medical adherence that was explained by self-compassion could be attributed to lower perceived stress. Overall, findings demonstrate that dispositional self-compassion is associated with better medical adherence among people with fibromyalgia, chronic fatigue syndrome, and cancer, due in part to lower stress. This research contributes to a growing evidence base indicating the value of selfcompassion for health-related behaviours in a variety of medical populations.