Unlike other personality traits or dispositions, self-compassion can be nurtured and is likely a driving source for physical activity. Emerging research has started to examine self-compassion in physical activity contexts; however, most existing studies were underpowered and overlooked the psycho-behavioural factors underlying the link between self-compassion and physical activity. In a sample of 569 UK adults (mean age = 41.92 years, SD = 13.70; 47.8% female), we examined the hypothesis that self-compassion’s positive influence on physical activity operates through reduced psychological distress and subsequently increased barrier self-efficacy. Results supported the prediction, with the positive influences of self-compassion being more prominent in more vigorous physical activity. The findings suggest that self-compassion is a good source of emotional resources (i.e., attenuated psychological distress) and confidence to overcome challenges and obstacles (i.e., increased barrier self-efficacy) in the context of physical activity. Future interventions and programs could consider incorporating self-compassion for physical activity adoption and maintenance.