--- - |2 Abstract Youth mentoring practitioners and researchers have shown a growing interest in determining the ways in which mentor–youth matching practices might influence the duration and effectiveness of mentoring relationships. The current project tested whether mentor–youth similarities at baseline, in terms of demographic variables and interests in certain activities (e.g., sports, art), predicted a longer duration of mentoring relationships. Analyses used baseline and follow‐up data from over 9,000 youth who participated in community‐based mentoring programs in the northeastern United States, as well as their volunteer mentors. Racial and ethnic similarity between mentor and youth was predictive of longer match duration. Moreover, a shared dislike of activities was associated with longer matches than either shared interests or discordant interests in activities. Findings have important implications for determining the ways in which mentor–youth matching practices influence the length and effectiveness of mentoring relationships. - Journal of Community Psychology, EarlyView.