ABSTRACT: Burnout is highly prevalent in residents. No randomized controlled trials have been conducted measuring the effects of Mindfulness-Based Stress Reduction (MBSR) on burnout in residents.To determine the effectiveness of MBSR in reducing burnout in residents.A randomized controlled trial comparing MBSR with a waitlist control group.Residents from all medical, surgical and primary care disciplines were eligible to participate. Participants were self-referred.The MBSR consisted of eight weekly 2.5-h sessions and one 6-h silent day.The primary outcome was the emotional exhaustion subscale of the Dutch version of the Maslach Burnout Inventory-Human Service Survey. Secondary outcomes included the depersonalization and reduced personal accomplishment subscales of burnout, worry, work-home interference, mindfulness skills, self-compassion, positive mental health, empathy and medical errors. Assessment took place at baseline and post-intervention approximately 3 months later.Of the 148 residents participating, 138 (93%) completed the post-intervention assessment. No significant difference in emotional exhaustion was found between the two groups. However, the MBSR group reported significantly greater improvements than the control group in personal accomplishment (p?=?0.028, d?=?0.24), worry (p?=?0.036, d?=?0.23), mindfulness skills (p?=?0.010, d?=?0.33), self-compassion (p?=?0.010, d?=?0.35) and perspective-taking (empathy) (p?=?0.025, d?=?0.33). No effects were found for the other measures. Exploratory moderation analysis showed that the intervention outcome was moderated by baseline severity of emotional exhaustion; those with greater emotional exhaustion did seem to benefit.The results of our primary outcome analysis did not support the effectiveness of MBSR for reducing emotional exhaustion in residents. However, residents with high baseline levels of emotional exhaustion did appear to benefit from MBSR. Furthermore, they demonstrated modest improvements in personal accomplishment, worry, mindfulness skills, self-compassion and perspective-taking. More research is needed to confirm these results.