Objective: This study examined past-2-week driving after marijuana use (DMU) and driving after having five or more drinks (D5D) during young adulthood, specifically focusing on associations between within-person change in social roles (living situation, marriage, parenthood, education, employment) and mediators (perceived risk, evenings out, and religiosity) from modal ages 19 to 30. Method: Multilevel analyses were conducted using survey data collected from 2013 to 2019 from 1,873 adults (1,060 women; total number of data collection waves = 7,037) participating in the longitudinal Monitoring the Future study. Results: Change across waves from not being married to married was associated with lower DMU likelihood at any particular wave both directly and via mediation through wave-level change in evenings out. Change in employment (not employed to employed full time) was associated with higher D5D likelihood at any particular wave both directly and via mediation through change in evenings out. Wave-level change in other social roles was indirectly associated with DMU/D5D likelihood via wave-level change in evenings out. Conclusions: Change in all social roles examined was associated with change in evenings out, which appears to be a primary, proximal predictor of young adult DMU/D5D. Improved understanding of how socialization change is associated with driving after substance use may strengthen efforts to reduce the harms associated with such driving behaviors. [ABSTRACT FROM AUTHOR]