Purpose: This project explored the efficacy of Dialectical Behavior Therapy (DBT) for young persons aging out of the Department of Children and Families (DCF) system. Methods: The project was conducted with participants at a Residential Program for “transitional youth,” who have serious emotional disturbance and emerging mental illness (N=15). The research method combined a post-test only comparison group design, with pretest, post-test observations for the DBT group. The research question explored the efficacy of DBT for this population, and used a mixed-method approach combining both quantitative and qualitative data collection. All participants received individual therapy, with 24/7 wrap-around residential services. The DBT intervention consisted of an additional two hours of weekly skills-training groups. The mean length of exposure to the DBT intervention was 12.4 months. The quantitative measures included The Modified Global Assessment of Functioning Scale (M-GAF), and The Purposeful Productive Activity and Quality of Life Scale (PPA-QOL). The qualitative portion of the study involved semi-structured interviews and focus groups. Results: Members of the DBT group improved from pretest to post-test, and when judged against the comparison group, in terms of global functioning, social relationships, and productive use of time or “intentionality,” but not in terms of vocational functioning. The qualitative data suggested that DBT group members used the groups to work on specific interpersonal relationship, emotion regulation, and distress tolerance skills, as well as to get feedback and support from others in the group. Conclusions: Because no previously published studies exist exploring the efficacy of DBT with transitional youth, these preliminary findings begin to fill in this knowledge gap. The potential implications of these findings for clinical practice may be to suggest DBT as a promising, evidence-based intervention for this vulnerable, and heretofore under-served population.