This longitudinal study examined the contribution of anxiety/depressive symptoms and lifetime and recent trauma exposure to substance use after residential substance abuse treatment among individuals with co-occurring disorders. Data were collected from adults at treatment entry and 6 and 12 months later. At treatment entry, nearly all participants reported lifetime trauma exposure, and over one third met criteria for posttraumatic stress disorder (PTSD). Over the follow-up, nearly one third of the participants were exposed to trauma. Lifetime trauma exposure and a diagnosis of PTSD at treatment entry were not associated with substance use over the follow-up. Trauma exposure and anxiety/depressive symptoms over the follow-up were associated with an increased likelihood of substance use. Gender did not moderate the association between trauma exposure and anxiety/depressive symptoms and substance use. These findings highlight the importance of monitoring for trauma exposure and symptoms of anxiety/depression to better target interventions and continuing care approaches to reduce the likelihood of posttreatment substance use in this population.