Problematic sexual behavior in youth represents a significant public health problem in need of evidence-based treatments. Unfortunately, such treatments are not available in most communities. This study used a mixed quantitative-qualitative approach to investigate the economics of the implementation of Problematic Sexual Behavior – Cognitive-Behavioral Therapy (PSB-CBT), an evidence-based treatment for problem sexual behaviors in youth. Youth (N = 413) participated in PSB-CBT at six program sites in youth service agencies across the United States. We used cost-effectiveness ratios (CERs) to compare the direct and indirect costs of PSB-CBT to self- and caregiver-reported youth clinical outcomes (i.e., problem sexual behavior as well as secondary behavioral health problems). CERs represented the cost of achieving one standard unit of change on a measure (i.e., d = 1.0). The design and interpretation of those quantitative analyses were informed by qualitative themes about program costs and benefits that were derived from interviews with 59 therapists, administrators, and stakeholders. CERs (i.e., $ per SD) were $1,772 per youth for problem sexual behavior and ranged from $2,867 to $4,899 per youth for secondary outcomes. These quantitative results, considered alongside the qualitative perspectives of interviewees, suggested that the implementation of PSB-CBT was cost-effective. The results were robust to uncertainty in key parameters under most, but not all, conditions. The results have important implications for decisions made by administrators, policymakers, and therapists regarding use of community-based approaches to address problematic sexual behavior of youth.