This study investigated the relationship between histories of childhood abuse and aggressive behaviors among adolescent girls involved in child welfare, and determined whether symptoms of post-traumatic stress and depression mediated this relationship. Participants were 237 girls ages 12-19 years. Overall, results indicated 89 % of the adolescents endorsed at least one aggressive behavior towards others. Specifically, 72.0 % engaged in physical aggression, 78.5 % engaged in non-physical aggression, and 51.5 % endorsed relational aggression. Greater severity of emotional and physical abuse were significantly associated with a higher frequency of aggressive behaviors. Sexual abuse was not significantly related to aggression. Post-traumatic stress and depression fully mediated the relationship between emotional abuse and aggression, controlling for race, service use, and living situation. The linkages between physical abuse and aggression were not mediated by either post-traumatic stress or depression. Findings suggest that among adolescent girls with histories of emotional abuse, post-traumatic stress and depression represent potential modifiable risk factors to target for reducing aggression.