Military personnel report significant and increasing mental health problems in the months following return from combat. Nevertheless, studies have not assessed the impact of mental health training with this at-risk population. The present study evaluated the efficacy of a prototype mental health training module designed for U.S. soldiers 3–6 months after returning from combat; the module was a component of the Battlemind Training system. Soldiers (N = 1,645) were randomly assigned by platoon to 1 hour of training or a survey-only control group. Baseline surveys were conducted immediately before training; a training satisfaction survey was administered immediately after training, and a follow-up survey was administered 6 months later. Immediate postsession surveys were conducted with 681 subjects, and follow-up surveys were conducted with 542 soldiers. The Battlemind Training module received positive ratings from participants, and those who received it reported significantly better adjustment in terms of posttraumatic stress disorder symptoms, depression, and life satisfaction at follow-up compared to those in the survey-only control group. Changes in attitudes about the stigma of seeking mental health care were found immediately posttraining, but not at follow-up. The findings demonstrate that brief mental health training can be effective in reducing mental health systems with at-risk occupational groups.