Teen dating violence (TDV) is a significant public health problem that can have lifelong consequences. Using a longitudinal, cluster randomized controlled trial (RCT), this study examines whether the "Dating Matters" comprehensive prevention model, implemented in middle school, prevented TDV and negative relationship behaviors and promoted positive relationship behaviors in high school (9th-11th grades), when compared with a standard of care intervention. "Dating Matters" includes programs for sixth to eighth grade youth and their parents, training for school staff, a youth communications program, and policy and data activities implemented in the community. Self-report survey data were collected from students in 46 middle schools that were randomly assigned to condition within site. Students completed two surveys (fall and spring) in each middle school grade and a single survey in the spring of each high school grade. This study examined self-reported TDV perpetration and victimization, use of negative conflict resolution strategies, and positive relationship skills in the high school follow-up. While varying patterns emerged, latent panel models demonstrated significant program effects for all outcomes. "Dating Matters" students reported 19% reduced risk for TDV perpetration, 24% reduced risk for TDV victimization, 7% reduced risk for use of negative conflict strategies, and 3% more use of positive relationship skills, on average across time and cohort, than standard of care students. On average, "Dating Matters," implemented in middle school, continued to be more effective at reducing TDV perpetration, TDV victimization, and use of negative conflict resolution strategies in high school than an evidence-based comparison program.