Mentoring is increasingly recognized as a critical element in supporting successful careers in academic research in medicine and related disciplines, particularly for trainees and early career investigators from underrepresented backgrounds. Mentoring is often executed ad hoc; there are limited programs to train faculty to become more effective mentors, and the few that exist have a dearth of empirical support of their impact. In 2013, we recruited 34 faculty from across the US engaged in HIV-related clinical research to participate in a 2-day Mentoring the Mentors workshop. The workshop included didactic and interactive content focused on a range of topics, such as mentor-mentee communication, leadership styles, emotional intelligence, understanding the impact of diversity (unconscious bias, microaggressions, discrimination, tokenism) for mentees, and specific tools and techniques for effective mentoring. Pre- and post-workshop online evaluations documented high rates of satisfaction with the program and statistically significant improvements in self-appraised mentoring skills (e.g. addressing diversity in mentoring, communication with mentees, aligning mentor-mentee expectations), as assessed via a validated mentoring competency tool. This is the first mentoring training program focused on enhancing mentors' abilities to nurture investigators of diversity, filling an important gap, and evaluation results offer support for its effectiveness. Results suggest a need for refinement and expansion of the program and for more comprehensive, long-term evaluation of distal mentoring outcomes for those who participate in the program.