Literature reviews on suicide prevention programs have presented conflicting results on the efficacy of school-based prevention programs. Gatekeeper training and peer helping are both recommended as part of a comprehensive school-based prevention program, yet there is no literary evidence of the systematic evaluation of gatekeeper training for peer helpers. This study evaluated the efficacy of such training with high school peer helpers using a repeated measures design. Significant gains in knowledge about suicide and skills for responding to suicidal peers were evident immediately after training and 3 months later. There was also a significant improvement in positive attitudes toward suicide intervention following training. Although there was no control group, the research offers tentative support for the efficacy of training peer helpers in suicide risk assessment and indicates the importance of additional training for peer helpers.