Background There is a variety of studies about the correlational relationship between personality, mindfulness and acceptance. However, there is no research about whether the personality affects the outcome of a mindfulness- and value-based (MAV) intervention, if the personality traits can in fact change along the intervention, and if the change in acceptance related skills explains this. Purpose The present study aimed to investigate these issues, and also if there were changes in personality traits or acceptance skills between or within groups. Methods The participants (n=102 in the intervention group, n= 90 in treatment as usual, i.e. TAU group) took part in a MAV intervention for job burnout, and their personality profiles were measured at pre-intervention (Time 1) and at follow-up (Time 3). Their acceptance skills were measured in Time 1 and post-intervention (Time 2) phases with a measure based on three questionnaires (ATQ-F, ATQ-B and AAQ-II). Results The intervention group significantly increased their acceptance skills compared to the TAU group skills in Time 2. Both groups significantly lowered their Neuroticism scores, and the intervention group had a significantly lower Neuroticism score compared to the TAU group in Time 2. Moreover, Extraversion and Conscientiousness increased in the intervention group. The change in acceptance skills mediated fully the change of Extraversion and Conscientiousness, and partially the change of Neuroticism. The personality traits did not explain the Time 2 score of acceptance in the intervention group, but in the TAU group there were three personality traits i.e. Neuroticism, Extraversion and Openness, that together with the Time 1 acceptance skills, explained the Time 2 acceptance skills. Conclusions According to these results, a MAV intervention can cause significant changes in acceptance skills and personality traits. Moreover, the personality may affect one’s acceptance skills, but the intervention may change its effect.