Research has shown insecure attachment style is associated with ineffective emotional regulation leading to maladaptive behaviors in adulthood. In the present study, we examined the association between attachment style and illicit substance use within a sample of adoptees (n=148). It was predicted that insecure attachment style would be associated with a higher incidence of lifetime illicit substance use and that perceived social support would mediate this association. Logistic regression analyses showed higher prevalence of illicit substance use among both insecure attachment groups as compared to the secure group. No difference was found between the two insecure types. Perceived social support was found to mediate the association between attachment style and illicit substance use for the insecure-preoccupied group only. The findings from the present study further implicate attachment style in the risk for illicit substance use, as well as preventions designed to identify those at risk for use.