While juvenile drug courts (JDCs) require treatment participation, youth and parent engagement in treatment cannot be mandated. We compared youths' and parents' self-reports of engagement in Risk Reduction Therapy for Adolescents (RRTA) and Treatment as Usual (TAU) in JDCs. Parents and youth receiving RRTA were more likely than those receiving TAU to report high engagement in treatment. High parent engagement in RRTA early in treatment predicted fewer missed appointments and lower youth substance use at 3 months. Emphasizing therapeutic techniques that increase parent engagement, as utilized in RRTA, could lead to improved participation and clinical outcomes in court-mandated treatment settings.