The current study investigated: (a) the relationships of exposure to the Adolescent Community Reinforcement Approach (A-CRA) with reductions in substance use, illegal activity, and juvenile justice system involvement in adolescents diagnosed with a substance use disorder, and (b) the pathways by which reductions in the target behaviors were achieved. This study is a secondary data analysis of longitudinal data from a large-scale implementation effort for A-CRA. The sample consisted of 1,467 adolescents who presented to substance use treatment and reported past-year engagement in illegal activity. Participants had an average age of 15.8 years (SD = 1.3) and were 25% female, 14% African American, 29% Hispanic, 35% Caucasian, 16% mixed ethnicity, and 6% other ethnicity. Path analyses provided support that participation in A-CRA had a significant, direct association with reduced substance use; a significant, indirect association with reduced illegal activity through reductions in substance use; and a significant indirect association with reduced juvenile justice system involvement through reductions in both substance use and illegal activity. In addition, post hoc analyses using a bootstrapping strategy provided evidence that reductions in substance use partially mediated the relationship between A-CRA and illegal activity.