Longitudinal research investigating the enduring impact of mindfulness training is scarce. This study investigates the six-year effects of a seven-week mindfulness-based course, by studying intervention effects in the trajectory of dispositional mindfulness and coping skills, and the association between those change trajectories and subjective well-being at six-year follow-up. 288 Norwegian medical and psychology students participated in a randomized controlled trial. 144 received a 15-hour mindfulness course over seven weeks in the second or third semester with booster sessions twice yearly, while the rest continued their normal study curricula. Outcomes were subjective well-being, and dispositional mindfulness and coping assessed using the Five Facet Mindfulness Questionnaire and the Ways of Coping Checklist. Analyses were performed for the intention-to-treat sample, using latent growth curve models. At six-year follow-up, students receiving mindfulness training reported increased well-being. Furthermore, they reported greater increases in the trajectory of dispositional mindfulness and problem-focused coping along with greater decreases in the trajectory of avoidance-focused coping. Increases in problem-focused coping predicted increases in well-being. These effects were found despite relatively low levels of adherence to formal mindfulness practice. The findings demonstrate the viability of mindfulness training in the promotion of well-being and adaptive coping, which could contribute to the quality of care given, and to the resilience and persistence of health care professionals.TRIAL REGISTRATION: Clinicaltrials.gov NCT00892138.