Using data from a 15-year longitudinal follow-up of a randomized controlled trial of a parenting-focused preventive intervention for divorced families (N = 240) with children aged 9–12, the current study examined alternative cascading pathways through which the intervention led to improvements in offspring’s perceived health problems, BMI, and cigarette smoking in emerging adulthood. It was hypothesized that the program would lead to improvements in these health-related outcomes during emerging adulthood through progressive associations between program-induced changes in parenting and offspring outcomes, including mental health problems, substance use, and competencies. Intervention-induced improvements in positive parenting at posttest led to improvements in mental health problems in late childhood/early adolescence, which led to lower levels of mental health and substance use problems as well as higher levels of competencies in adolescence, which led to improvements in the health-related outcomes. Academic performance predicted all three health-related outcomes and other aspects of adolescent functioning showed different relations across outcomes. Results highlight the potential for intervention effects of preventive parenting interventions in childhood to cascade over time to affect health-related outcomes in emerging adulthood.