Coordination of mental health services in children with serious emotional disturbance (SED) has shown a preliminary relationship to positive outcomes in children. Yet, research in this area is sparse. Therefore, the relation between service coordination activities and adaptive functioning was examined for 51 children SED who were treated in the school-based Intensive Mental Health Program for elementary school students (IMHP; average treatment length was 12 months; mean age 9.37 at intake). Systematic review of detailed case records identified 16,669 episodes of service coordination that could be coded reliably for frequency, quality, and purpose (planning, linking, monitoring) of the service coordination component. Adaptive functioning was measured by Child and Adolescent Functional Assessment Scale (CAFAS) ratings and daily points earned on the behavior management system of the IMHP at intake, 6, 12 months, and discharge. Findings indicated that the frequency, quality, and purpose of the service coordination component varied from case to case and by time in treatment. Although service coordination activities overall decreased as treatment progressed, concentrated high quality service coordination (measured by frequency, quality, and component of service coordination) consistently predicted improved functioning on both CAFAS ratings and daily points earned. Results have both practice and policy implications for training interagency teams and clinicians on when and how to optimally coordinate services.