The Communities That Care (CTC) prevention system seeks to build community capacity for a science-based approach to the promotion of healthy youth development. Prior research shows the positive effects of CTC on youth protective factors during CTC implementation. This research tests sustained effects of CTC on youth protective factors 1 year after external support to communities for CTC implementation ended.Data come from a community-randomized trial of CTC in 24 communities across 7 states. A panel of 4,407 youth in CTC and control communities was surveyed annually from Grade 5 through Grade 10. Youth reported their exposure to protective factors identified in the social development model. Global test statistics are calculated to examine effects of CTC across 15 protective factors in 5 domains (community, school, family, peer, and individual) assessed in Grade 10, 1 year after study support for CTC implementation ended. Analyses also examine variation in sustained effects by gender and baseline risk levels.Global effects of CTC on protective factors across all domains are not sustained in Grade 10. However, sustained domain-specific effects are observed in the individual domain for males, in the peer domain for females, and in the individual domain for youth with low-to-medium risk at baseline.Greater emphasis on strengthening protective factors during high school might be needed to sustain broad effects of CTC on protective factors observed during middle school.