 This study evaluated the effectiveness of a hybrid mentor training program which consisted of an online module followed by workshops based on the entering mentoring EM curriculum. The results showed that the intervention, 6.5 hours, produced significant improvements in all outcomes, including skills gains on par with those reported previously for the ATAR EM model. Additionally, mentors valued the synergy of the blended learning format, noting the unique strengths of each modality and specific benefits to completing a foundational online module before in-person engagement. This study supports the use of e-learning approaches, both as standalone curricula or as a component of hybrid implementation models, for the professional development of research mentors. This article was authored by Anne-Marie Webbermaine, Janet Shannadling, Alexander M. Kaizer, and others.