BACKGROUND: The need for mentorship in aging research among postdoctoral trainees and junior faculty across medical disciplines and subspecialties is increasing, yet senior personnel with expertise in aging are lacking to fulfill the traditional dyadic mentorship role. Facilitated peer mentorship is grounded in collaborative work among peers with the guidance of a senior mentor. METHODS AND RESULTS: We evaluated the Columbia University Mentor Peer Aging Research (CoMPAdRE) program, an interprofessional facilitated peer mentorship program for early stage investigators, using the Reach Effectiveness Adoption Implementation and Maintenance framework (RE-AIM). Reach: A total of 15 participants, of which 20% were women, from five states and across six medical specialties participated. Effectiveness: Participants published 183 papers, of which more than 20% were collaborative papers between CoMPAdRE mentees or mentees-mentor. Participants reported developing skills in negotiation, navigating the academic role, organizing a seminar, management, and leadership over the course of the program. According to the qualitative findings, the most important components of the program included alignment around the aging, learning from national leaders, developing leadership skills and career networking. Adoption: Individual-level factors included selecting participants with a research track record, willingness to sign a compact of commitment and involvement in shaping the program. An institutional-level factor that facilitated program adoption included strong commitment from department leaders. Implementation: The program cost $3,259 per participant. Maintenance: CoMPAdRE is being maintained and currently incorporating a second cohort of mentees. CONCLUSION: This RE-AIM evaluation provides lessons learned and strategies for future adoption, implementation, and maintenance of an aging-focused facilitated peer mentorship program. J Am Geriatr Soc 67:804–810, 2019.