Background - The reciprocal relationship between crime and substance use is well known. However, when examining this relationship, no study to date has disaggregated between- and within-person effects, which represents a more methodologically sound and developmentally-appropriate analytic approach. Further, few studies have considered the role of social risk (e.g., deviant peers, high-risk living situa-tions) in the aforementioned relationship. We examined these associations in a group of individuals with heightened vulnerability to substance use, crime and social risk - emerging adults (aged 18–25 years) in substance use treatment. Methods - Participants were 3479 emerging adults who had entered treatment. We used auto-regressive latent growth models with structured residuals (ALT-SR) to examine the within-person cross-lagged association between crime and substance use and whether social risk contributed to this association. A taxonomy of nested models was used to determine the structural form of the data, within-person cross-lagged associations, and between-person associations. Results - In contrast to the extant literature on cross-lagged relations between crime and substance use, we found little evidence of such relations once between- and within-person relations were plausibly disaggregated. Yet, our results indicated that within-person increases in social risk were predictive of subsequent increases in crime and substance use. Post-hoc analyses revealed a mediation effect of social risk between crime and substance use. Conclusions - Findings suggest the need to re-think the association between crime and substance useamong emerging adults. Individuals that remain connected to high-risk social environments after finishing treatment may represent a group that could use more specialized, tailored treatments.