The goal of this study was to investigate moderators of mindfulness training. The present study employed a brief form of mindfulness training with moderately distressed participants. Psychological distress was measured before and after a five-session mindfulness intervention. Two hypothesized moderators of treatment outcome, discomfort with emotion and mindfulness were measured before the intervention. Consistent with previous research, the brief mindfulness intervention was associated with reductions in psychological distress with a large pre-post effect size. Importantly, reductions in distress were significantly moderated by discomfort with emotion. Individuals reporting the most discomfort with emotion showed less reduction in distress after the mindfulness intervention. Results highlight the importance of investigating moderators of mindfulness intervention outcome.