Over half of young adults have cohabited, but relatively little is known about the role delinquency and substance use play in youths’ odds of cohabiting as well as the implications of cohabitation for early adult offending and substance use. This study focuses on the reciprocal relationship between cohabitation during late adolescence and young adulthood and self-reported offending and substance use. Using longitudinal data, we find that net of traditional predictors, delinquency involvement is associated with increased odds of cohabitation and cohabiting at younger ages while substance use is not related to cohabiting during early adulthood. Further analysis indicates that cohabitation is associated with lower reports of substance use. However, cohabitation is not associated with self-reported offending. The results help unravel the connection between cohabitation experience, offending and substance use, and early adult outcomes.