This study tested whether effects of a preventive intervention delivered in elementary school showed benefits for the young adult offspring of intervention recipients over 20 years later. The Raising Healthy Children (RHC) intervention, trialed in 18 public schools in Seattle, Washington, from 1980-1986 (grades 1-6), sought to build strong bonds to family and school to promote school success and avoidance of substance use and illegal behavior. Four intervention groups were constituted: full, late, parent training only, and control. Participants were followed through 2014 (age 39 years). Those who became parents were enrolled in an intergenerational study along with their oldest offspring (10 assessments between 2002 and 2018). This study includes young adult offspring (ages 18-25 years; n = 169; 52% female; 4% Asian, 25% Black, 40% multiracial, 4% Native American, 2% Native Hawaiian/Pacific Islander, 25% White, and 14% Hispanic/Latinx) of participants in the original RHC trial. Offspring outcome measures included high school noncompletion, financial functioning, alcohol misuse, cannabis misuse, cigarette use, criminal behavior, internalizing behavior, social skills, and social bonding. A global test across all young adult outcome measures showed that offspring of parents who received the full RHC intervention reported better overall functioning compared to offspring of control group parents. Analyses of individual outcomes showed that offspring of full intervention group parents reported better financial functioning than offspring of control group parents. Findings show the potential of universal preventive interventions to provide long-term benefits that reach into the next generation. ClinicalTrials.gov Identifier: NCT04075019; retrospectively registered in 2019.