Over a 12-year period, this study examined the effects of the Family Check-Up preventive intervention model on both observed and self-reported parenting behaviors of mothers and fathers as well as how those parenting behaviors were associated with young adult antisocial behavior. Teachers identified 641 early adolescent youth from school settings to be at elevated risk for the development of externalizing behavior and/or substance use. These youth and their families were randomly assigned to the Family Check-Up intervention model (consisting of an adaptive, multi-tiered model of support, including a school-based family resource room, the Family Check-Up, and targeted follow-up services) or a control condition. Using an intent-to-treat approach, the Family Check-Up intervention model positively impacted mothers' observed parenting approximately 5 years later in middle adolescence but was not associated with changes in fathers' observed or self-reported parenting. Mothers' observed adaptive parenting and fathers' self-reported adaptive parenting in middle adolescence were associated with lower risk for young adult antisocial behavior. The cascading effects of brief, family-focused interventions are discussed along with implications for the measurement of parenting in mothers and fathers in the context of preventive intervention trials.