This prospective, mixed-methods study investigated how the nature of joint activities between volunteer mentors and student mentees corresponded to relationship quality and youth outcomes. Focusing on relationships in school-based mentoring programs in low-income urban elementary schools, data were obtained through pre–post assessments, naturalistic observations, and in-depth interviews with mentors and mentees. Adopting an exploratory approach, the study employed qualitative case study methods to inductively identify distinctive patterns reflecting the focus of mentoring activities. The activity orientations of relationships were categorized according to the primary functional role embodied by the mentor and the general theme of interactions: teaching assistant/tutoring, friend/engaging, sage/counseling, acquaintance/floundering. Next, these categories were corroborated by comparing the groups on quantitative assessments of relationship quality and change in child outcomes over time. Relationships characterized by sage mentoring, which balanced amicable engagement with adult guidance, were rated most favorably by mentees on multiple measures of relationship quality. Furthermore, students involved in sage mentoring relationships showed declines in depressive symptoms and aggressive behaviors. For disconnected pairs (acquaintances), students reported more negative relationship experiences. Findings suggest effective mentoring relationships represent a hybrid between the friendly mutuality of horizontal relationships and the differential influence of vertical relationships.