The objectives of this study were to examine outcomes of the Minnesota D.A.R.E. Plus Project on violence-related behaviors among middle school students and mediation analyses that test how the intervention was effective in reducing physical and verbal violence. Twenty-four schools were randomly assigned to the D.A.R.E. middle school curriculum, the D.A.R.E. Plus multicomponent intervention, or control. The study cohort completed a self-report questionnaire at baseline and two follow-ups. The results showed that boys had higher rates of violence and victimization than girls. The D.A.R.E. Plus program was more effective in preventing violence among boys than among girls. It appears that the small behavioral effect that D.A.R.E. Plus did demonstrate on physical and verbal violence among boys was entirely mediated by a decrease of norms that support violence, an increase in outcome expectancies about being violence-free, and an increase in parental consequences for fighting.