Objectives: The study aimed to investigate the pre-to-post effects of mindfulness training on school teachers’ psychological and professional well-being, as well as to explore the moderating role of temperament and character on these effects. Method: An 8-week mindfulness-based intervention was delivered via internet-based group meetings to Italian teachers (n = 139), who were assessed within two weeks before and after the intervention with self-report measures of emotional distress (Hospital Anxiety and Depression Scale), interoceptive awareness (Multidimensional Assessment of Interoceptive Awareness), and professional efficacy (Teachers’ Sense of Efficacy Scale), as well as with the Temperament and Character Inventory. A control group of teachers (n = 47) was tested with the same measures in two temporally-matched sessions. Results: Analysis of variance showed positive intervention effects on anxiety (medium effect size), on six of the eight dimensions of interoceptive awareness (medium-to-large effect size) and on two of the three scales of professional efficacy (small-to-medium effect size). Moderation analysis identified the following effects of temperament and character on outcomes: (1) reduced anxiety only for higher baseline reward dependence, or lower-to-middle baseline self-directedness; (2) improved interoceptive attention regulation specifically for middle-to-higher baseline persistence; (3) improved teacher efficacy for student engagement only for lower baseline self-transcendence. Conclusions: The study shows the positive effects of mindfulness training on teachers' psychological and professional well-being. It also highlights the importance of considering the impact of temperament and character dimensions on these effects, for example for developing effective mindfulness-based interventions for teachers. Future research should explore potential mechanisms of action underlying the observed effects and evaluate them in the long term. Preregistration: This study is not preregistered.
