The problem of adolescent drug use places a huge toll on society and a heavy burden on the criminal justice system. Despite the ability of therapeutic communities (TCs) to lower drug relapse, a great deal remains unknown in terms of how the process of treatment actually works for adolescents. Using data collected as part of the Drug Abuse Treatment Outcomes Studies–Adolescents, this study examines the direct and indirect relationship between therapeutic engagement and posttreatment substance use. Though there are few direct effects of therapeutic engagement on substance use, findings suggest that those more engaged in treatment are more likely to complete treatment and, therefore, less likely to use substances. This suggests that instruments that evaluate therapeutic engagement are important in assessing involvement in treatment, and that programming designed to engage the adolescents in TC treatment should be utilized to reduce the risk of posttreatment relapse.