Objective: This study tests a Stabilizing Group Treatment protocol, designed for the management of the long-term sequelae of child abuse, that is, Complex Posttraumatic Stress Disorder (Complex PTSD). Evidence-based treatment for this subgroup of PTSD patients is largely lacking. This stabilizing treatment aims at improving Complex PTSD using psycho-education and cognitive behavioral interventions. Method: Thirty-six patients with a history of childhood abuse, Complex PTSD and severe co-morbidity entered a 20-week treatment with pre-, post-, and follow-up-assessments. Results: Improvement was found for PTSD and borderline symptoms. Post-treatment 64% and after 6 months 78% of patients no longer met criteria for Complex PTSD. Conclusions: This open study indicates both the feasibility of investigating treatment outcome and the initial efficacy of stabilizing group treatment in severely ill patients with Complex PTSD related to childhood abuse. (Contains 2 tables.)