Background : Patients with PTSD related to childhood-abuse often experience additional problems such as emotional dysregulation and interpersonal difficulties. Psychotherapy focused on stabilization of symptoms, emotion-regulation, and skills training has been suggested as a treatment for this patient population, either as preparation for further treatment or as a stand-alone intervention. Objective : The present study tests the efficacy of treatment using a group-protocol for stabilizing treatment delivered adjunct with conventional individual therapy. Methods : In a delayed-treatment design with switching replication, a clinically representative sample of 89 patients with PTSD and histories of childhood abuse were randomly assigned to either 20-week stabilizing group treatment or a corresponding waiting-period, both adjunct with conventional individual therapy. After the waiting-period, patients in the control condition were offered group treatment. The primary outcome was psychosocial functioning, measured with interview – assessed Global Assessment of Functioning (GAF), while secondary outcome was self-reported PTSD symptoms. These were measured before treatment, after treatment and at 6 months follow up. The trial was preregistered at Clinical Trials (NCT02450617). Results : We found large within-group effect sizes in both conditions on GAF and moderate effects on PTSD symptoms. Linear mixed-models did not indicate significant differences in treatment trajectories between conditions. Conclusion : Stabilizing group treatment focused on emotional-regulation and skills-training does not improve outcomes beyond individual-treatment alone, and should not be recommended as first-line treatment for this patient-group