Prior work indicates that substance use is related to adolescent marriage. We describe two different processes that may account for this relationship and hypothesize patterns of association that would be consistent or inconsistent with each. Using data from a study that followed west coast youth from 7th grade to young adulthood N3,324, we assessed the effects of cigarette, alcohol, and marijuana use in 7th and 10th grade on the probability of marriage prior to age 20. When gender, race, and SES were controlled, cigarette use in adolescence, but not other substance use, was associated with early marriage. Low educational attainment and early unwed parenthood each uniquely mediated this association. These results suggest that the link between substance use and early marriage reflects a disposition toward risky or unconventional behavior, not the judgment impairing effects of drug and alcohol use.