High-quality youth development programs can serve as relationship-rich spaces where youth develop a sense of belonging and meaningful connections with caring adults and peers. The pathways between strong relationships and youth’s sense of belonging within these settings remains unexplored, particularly among PYD programs who serve youth from low-income communities. Therefore, this study examined the bidirectional pathways between developmental relationships with program peers and program staff and youth’s sense of belonging. The study included 194 youth (ages 8–17; 75% youth of color; 46% female) who participated in a program designed to provide youth living in low-income households with trusting relationships and greater access to year-round enrichment opportunities. Utilizing survey data across three time points, findings show how youth’s sense of belonging and developmental relationships with program peers led to stronger developmental relationships with program staff over time. Findings highlight important implications for the role of program peers within positive youth development programs.