We report the results of a short programme of mindfulness training administered to adolescent boys in a classroom setting. Intervention and control groups (N = 155) were compared on measures of mindfulness, resilience and psychological well-being. Although the overall differences between the two groups failed to reach significance, we found that within the mindfulness group, there was a significant positive association between the amount of individual practice outside the classroom and improvement in psychological well-being and mindfulness. We also found that the improvement in well-being was related to personality variables (agreeableness and emotional stability). Most students reported enjoying and benefiting from the mindfulness training, and 74% said they would like to continue with it in the future. The results of this preliminary study are encouraging. Further work is needed to refine the training programme and undertake a definitive randomised controlled trial, using both subjective and objective outcome measures, with long-term follow-up.