Children in foster care are frequently affected by adverse childhood experiences (ACEs) resulting in predictable and significant cognitive, developmental, and physical changes (Forkey, & Szilagyi, 2014). In British Columbia, there are an estimated 7,000 children in foster or out-of-home care and an estimated 62,000 across Canada (Canadian Child Welfare Research Portal, 2017). The Complex Care and Intervention (CCI) program is a developmentally driven program designed for children who have experienced trauma and exhibit significant emotional, behavioral and interpersonal difficulties. PURPOSE: The purpose of this study was to evaluate the impact of the CCI on childhood functional development, using the formalized Functional Development Assessment (FDA). METHODS: A retrospective, pre/post observational design was used to analyze de-identified participant data (n=180). Data were obtained from Complex Trauma Resources, British Columbia, Canada. RESULTS: The analysis revealed a statistically significant positive change in all seven domains of the FDA between entry and exit of the program, as well as in the overall mean score. Additional analysis revealed that the CCI model is effective regardless of the variables of age, gender, and race. Metrics related to the validation of the FDA are reported. CONCLUSION: The CCI mitigates disruptive behaviors and developmental lags in children who experience complex trauma. These results may further compel practitioners to utilize trauma-informed care modalities to broaden their approach in treating the common and predictable trauma-related difficulties of children with ACEs in foster care.