The present study uses the Interactive Systems Framework (ISF) to understand how general capacity influences the implementation of prevention programs in afterschool settings. Eight afterschool sites received the Good Behavior Game (GBG) intervention, a program designed to foster supportive behavioral management and positive youth behavior. In line with the Prevention Support System component of ISF, the intervention afterschool staff were trained and received weekly on-site support from coaches in implementing the GBG. It was found that GBG implementation scores were greatest in afterschool programs that rated high on both organizational- and community-levels of general capacity; high scores on only one level of general capacity resulted in lower implementation scores. Thus, afterschool sites that were more organized, maintained adequate facilities, and developed strong linkages to individuals or organizations in the community scored highest in implementation fidelity and quality. This study highlights the importance of considering interactions among multiple levels of general capacity in efforts to promote evidence-based practices in afterschool settings. Caution should be taken in generalizing findings due to the small sample in this study.