Despite significant advances in knowledge and availability of evidence-based models for child traumatic stress, many children simply do not complete treatment. There remain notable gaps in the services research literature about treatment completion among youth, particularly those who have experienced trauma and related sequelae. This study investigated the linkages among child physical and sexual trauma, posttraumatic stress disorder (PTSD) symptomatology, and treatment completion utilizing a clinical sample drawn from a large database from community treatment centers across the United States specializing in childhood trauma. Results from regression analyses indicated that neither the experience of sexual nor physical trauma directly predicted successful treatment completion. The links between sexual trauma and treatment completion, however, were mediated by PTSD avoidance symptoms. Children and youth experiencing sexual trauma reported higher levels of avoidance symptoms that were, in turn, significantly associated with a lower likelihood of completing trauma-focused mental health treatment. Practice implications are discussed and include strategies for clinicians to intervene during pivotal points of treatment to improve rates of service utilization and treatment completion.