Schools have the unique opportunity to identify and refer youth at risk for suicide. School-based gatekeeper training programs aim to improve staff's ability to talk to students about mental health concerns and refer them for an assessment. Unfortunately, progress in evaluating the available programs has been limited. In fact, the popular and widely used More Than Sad program has received no rigorous evaluation to date. This study sets out to evaluate the effectiveness of the More Than Sad program in a quasi-experimental, wait-list control design with a large number of school personnel, across geographically diverse communities. Fourteen school districts with over 1475 school personal received the training. A standardized assessment tool was used before and after the training and two months later. Half of the schools served as a wait list control before receiving the treatment. Results. Compared to wait-listed staff, school personal who received the training reported a significant increase in knowledge, preparedness, self-efficacy, and likelihood to refer. Self-reported and actual referral behavior also increased both for those that had made referrals in the past and those that had not. Gains were maintained at 2-month follow-up. More Than Sad can effectively improve suicide literacy and willingness to refer youth at risk for suicide to school mental health resources. With 90% of the training pre-recorded on DVDs, future research should explore implementation feasibility and effectiveness.