Physical activity-based positive youth development (PYD) programs are associated with improved self-esteem and prosocial behavior (McDonough et al., 2013; Ullrich-French et al., 2013). Such active approaches to building psychological strengths also have potential to reduce health risk behaviors such as substance use and gang participation (Meyer et al., 2012; Snyder, 2014). We examined whether positive social relationships with staff and peers in a 20-day summer physical activity-based PYD program for youth from low-income families predicted reduced intentions for health risk behaviors, beyond the effect of relationship quality outside of the program. A cross-sectional survey of 331 youth (154 girls, 177 boys) aged 7–15 (M=10.6 SD=1.8) was conducted. Youth self-reported the quality of relationships with peers and staff in the program, peers outside of the program, and intentions to use cigarettes, alcohol, and illegal drugs, and participate in gangs during adolescence. Data were analyzed using regression approaches. This relatively young sample reported intentions to use cigarettes (5.4%), alcohol (13.9%), illegal drugs (7.1%) and join a gang (7.1%) as a teenager. Negative peer influence (B = .26) and peer support outside the program (B = -.13) significantly predicted intentions. Supportive relationships with staff (but not peers) in the PYD program predicted significant additional variance in intentions to engage in health risk behaviors (B = -.11; F(4, 300) = 11.41, R2= .13, p< .01). Research examining whether positive relationships with program staff are a mechanism to reduce health risk behaviors in youth is a potential avenue for demonstrating effects of PYD programs on youth in their lives outside of such programs.