Mentoring is an important aspect of professional development, but can it advance substance use disorder skills in a national, interdisciplinary fellowship program? This evaluation study used a telephone survey to examine the influence of distance mentoring, interdisciplinary mentoring, and mentor functions on fellows' satisfaction, learning and academic achievements. Based on responses from 36 fellows (92%), this study found high rates of satisfaction with mentors, learning, skill acquisition, and indications of changes in teaching practice. Group comparisons showed geographic distance was not a significant factor in mentoring outcomes, while same-discipline matches and select mentor functions were associated with more positive outcomes. (Contains 4 tables.)