A large body of prior research has demonstrated a clear link between family support and desistance from substance use during reentry. Emerging research also suggests that family conflict may play an independent role in this process. Accordingly, this study moves towards an understanding of how baseline between-individual differences in both family support and conflict prior to release interact with within-individual change in the respective constructs to affect substance use during the reentry time period. Results of cross-lagged dynamic panel models examining four waves of the Serious and Violent Offender Reentry Initiative data demonstrate baseline between-individual differences and within-individual changes in family conflict, but not support, significantly relate to polysubstance use. While these results suggest that families play a criminogenic role in reentry, a series of interaction terms demonstrates that within-individual increases in family support can help offset the negative influence of family conflict.