PROBLEM: There is evidence that peer-support programs can improve mental health indices and help-seeking behavior among students in some secondary school and university settings and that mindfulness can improve mental health in medical students. Peer-led programs have not been formally assessed in a medical student population, where psychological issues exist and where it has been shown that students approach peers for help in preference to staff members or professional services. INTERVENTION: Medical students elected peer leaders who underwent training and then provided the intervention. The peer leaders provided support to students in the intervention group, as well as offering teaching in mindfulness meditation. CONTEXT: An exploratory study was conducted with 2nd- and 3rd-year medical students at 1 medical school in New Zealand randomized into 2 groups. In addition to existing mental health resources, intervention participants received a program including peer support and peer-taught mindfulness practice. Study participants not offered the intervention participants could use existing mental health resources. Primary measures included depression (PHQ-9) and anxiety (GAD-7) scores. Secondary measures were quality of life, resilience (15-item resilience scale), academic self-concept, and motivation to learn, assessed at baseline and 6 months. OUTCOME: Of the 402 students eligible, 275 (68%) participated and 232 (58%) completed the study. At baseline, 53% were female and mean age was 21 years (SD = 3)-PHQ-9 score (M = 5.2, SD = 3.7) and GAD-7 score (M = 4.5, SD = 3.4). Twelve peer leaders were elected. There was good participation in the intervention. One fourth of intervention students used the face-to-face peer support and more than 50% attended a peer social event and/or participated in the mindfulness program. Although improvements in mental health were seen in the intervention group, the difference between the intervention and nonintervention groups did not reach statistical significance. LESSONS LEARNED: Although evidence exists for effectiveness of peer support and mindfulness in other contexts, this exploratory study was not able to show a statistically significant effect. Future studies could consider using a longer training period for the peer leaders, as well as targeting the study population to those most likely to benefit such as those with poorer mental health, or using a more intensive intervention or larger sample size. A cluster randomized study design would also reduce the risk of contamination.