The Influence of Youth Gender and Complex Trauma on the Relation Between Treatment Conditions and Outcomes in Therapeutic Residential Care – Complex trauma (CT) is the experience, or witness, of prolonged abuse or neglect that negatively affects children’s emotional and psychological health. Youth in residential care experience higher incidences of complex trauma than youth in community-based care, with notable gender differences and presentation of psychological symptoms. This study examined the effects of trauma-informed residential care and the relation between CT and gender. A sample (n = 206) from an evaluation of a youth psychiatric residential facility in the Midwest that transitioned from a traditional care model to a trauma-informed care model was used. A hierarchical regression was used to model the main effects of model of care, gender, CT, length of stay, and crisis response on treatment outcomes; and the moderating effects of gender and CT. The results support the high prevalence of CT in residential care populations. The final model explained 30.2% of the variance with a statistically significant interaction between gender and length of stay in treatment, indicating that longer lengths of stay in treatment are associated with less change in functional impairment for girls than boys. Youth gender and prior trauma are important factors to consider when monitoring experiences and treatment outcomes in youth residential care.