Physical activity-based positive youth development (PYD) programs are designed to nurture personal and social assets in youth, and in underserved populations, often provide unique opportunities for physical activity and mentoring. Supportive relationships with peers and adults in such programs are associated with positive changes in developmental outcomes (Ullrich-French, McDonough, & Smith, 2012). In this case study, we examined youths’ and staff members’ perspectives on interpersonal relationships within a physical activity-based PYD program, their understanding of what experiences and interactions within the program help or hinder forming high-quality relationships, and their perspectives on how those relationships affect youth and transfer to contexts outside of the PYD program. We interviewed 20 youth and 6 program staff about their perspectives on social experiences in the PYD program, and conducted follow-up interviews with 10 youth participants 8 months later. We developed a figure describing youth and staff perspectives of program context factors, and how elements of interpersonal relationships among youth and between youth and staff affect youth intra- and interpersonal assets, and transfer to community contexts such as home, neighborhoods, and school. These findings provide insight into ways to promote positive social relationships in PYD programs in ways that are meaningful to youth.