BACKGROUND: Mindfulness-based interventions are well-established in the field of psychotherapy, and such interventions have also gained increased attention in the field of sport psychology, either to cope with psychological pressure or to improve an athlete's performance. The goal of the present study was to examine whether a Mindfulness-Acceptance-Commitment (MAC) program could increase self-compassion and grit among elite female athletes compared to an active control condition. To this end, we performed a randomized trial among female adult athletes. METHODS: Forty female adult athletes (M RESULTS: Dimensions of mindfulness, self-compassion and grit improved over time, but more so in the Mindfulness-Acceptance-Commitment condition compared to the active control condition. Improvements remained stable from the study end to follow-up. CONCLUSIONS: While the active control condition improved dimensions of mindfulness, self-compassion and grit among female adult athletes, improvements were much stronger in the Mindfulness-Acceptance-Commitment condition. Importantly, improvements in the Mindfulness-Acceptance-Commitment condition remained stable over a time lapse of four weeks at follow-up after study completion, suggesting that the Mindfulness-Acceptance-Commitment intervention appeared to improve cognitive-emotional learning processes.