A growing body of literature suggests that parenting practices characterized by careful monitoring, firm and consistent limit setting, and nurturing communication patterns with children are protective against adolescent substance use and other problem behaviors. Family-based prevention programs that promote these behaviors can be an effective way to prevent adolescent substance use. However, low participation rates remain problematic for many such programs, particularly programs that require parents to attend scheduled meetings outside the home. The purpose of this study was to determine the efficacy of a newly developed substance use prevention program when self-administered at home by parents of middle school students. As part of a randomized trial, 338 parents of middle school students either received the parent prevention program or served as control group participants. Parents completed self-report surveys at home that assessed parenting behaviors at pre-test, post-test, and one-year follow-up time points. A series of mixed model ANCOVAs were conducted, examining the post-test and one-year follow-up means for the parent outcomes, controlling for pre-test levels on these outcomes. Analyses showed that at the post-test assessment, intervention parents reported significant increases relative to controls in appropriate role modeling, disciplinary practices, family communication, and parental monitoring skills. At the one-year follow-up assessment, intervention effects on family communication skills remained significant and effects on parental role modeling were marginally significant. This study shows that a theoretically rich prevention program can be effectively self-administered by parents at home and improve key parenting skills that have been shown to prevent adolescent substance use.