Complex trauma (CT) results from exposure to severe stressors that occur within the caregiver system, are chronic, and largely begin in childhood or adolescence. This article describes the evidence-informed treatment of a 9-yearold female with chronic CT symptoms, resulting from longterm sexual, physical, and psychological abuse within her family. Treatment lasted 17 months and followed an assessment-driven, phase-based process. This process was flexibly implemented based on the unique circumstances of the case, while remaining consistent with the intent of the treatment models. Pre-to post-treatment data indicated significant reductions in trauma-related symptoms. Verbatim clinical vignettes illustrate specific interactions between family members and therapists, as well as interventions related to the treatment.