Complex training interventions can benefit from the RE-AIM (Reach, Effectiveness, Adaptation, Implementation, Maintenance) program evaluation framework because it considers various implementation factors like settings, facilitators, and adaptations that lead to outcomes like broadening participation. We demonstrate how to use RE-AIM with a complex mentor-training program called SCOARE (Scientific Communication Advances Research Excellence) to improve understanding of how program implementation leads to improved mentor skills that help broaden participation in the biomedical research workforce.