Overview: One recently completed randomized controlled trial (RCT) demonstrated the effectiveness of a doctor–office collaborative care (DOCC), relative to enhanced usual care (EUC), for pediatric behavior problems and attention-deficit/hyperactivity disorder. In this study, we sought to extend the literature by incorporating a cost-analysis component at the conclusion of the aforementioned trial. To our knowledge, it was the first study to examine whether the DOCC model leads to lower costs of mental health services for children. Method: Financial records from the RCT provided cost information about all the 321 child study participants in the 6-month intervention period, and claims data from insurance plans provided cost information about community mental health services for 57 children, whose parents consented to release their claims data, in both pre- and postintervention periods. Both descriptive and multivariate analyses were performed. Results: The DOCC group had higher intervention costs, but the cost per patient treated in the DOCC group was lower than the EUC group during the 6-month intervention period. In terms of costs of community mental health services, although the 2 groups had similar costs in the 6 months before the RCT intervention, the DOCC group had significantly lower costs during the 6-month intervention period and 6 or 12 months after the intervention, but not in the 18 or 24 months after the intervention. Discussion: The DOCC model has the potential for cost savings during the intervention period and the follow-up periods immediately after the intervention while improving clinical effectiveness.