Strengths can have a potent effect in mitigating the impact of trauma on mental health needs and functioning. Yet, evidence is limited on the role that strengths may have in ameliorating trauma-related or mental health symptoms over time. Providing a comprehensive assessment that includes strengths, as well as needs, is an important step in making appropriate service recommendations for youth in child welfare. This study assessed 7,483 children and adolescents entering an intensive stabilization program through the Illinois child welfare system. The interaction of individual, child strengths in relation to complex trauma exposure, traumatic stress symptoms, risk behaviors, and other mental health needs were examined. Results indicated strengths are relatively stable over time and inversely associated with several negative outcomes, including risk behaviors (−.32, p < .001), emotional/ behavioral needs (−.33, p < .001) and overall functioning (−.47, p < .001). Traumatic stress symptoms were also related to increases in these negative outcomes. Overall, strengths had a buffering effect on traumatic stress symptoms and outcomes over time. The role of strengths in relation to traumatic stress symptoms, however, was less consistent. Youth with histories of complex trauma exposure had significantly fewer useable strengths than youth without this exposure. However, strengths improved for both youth with and without complex trauma exposure over the course of stabilization services. These findings suggest that early identification and development of child strengths can mitigate risk-taking behaviors, mental health, and functional difficulties among youth in the child welfare system. Implications for more targeted trauma-informed and strengths-based assessment, and treatment/service planning are discussed.