Dialectical behavior therapy for posttraumatic stress disorder (DBT-PTSD) is tailored for adults with PTSD from childhood sexual abuse (CSA). It uses principles from DBT and trauma-focused cognitive–behavioral approaches. To evaluate acceptance and safety, the authors treated 29 women with chronic CSA-related PTSD plus at least one other comorbid diagnosis. The Posttraumatic Diagnostic Scale (PDS), Symptom Checklist 90-Revised, Beck Depression Inventory, and State Trait Anxiety Inventory were administered prior to, at the end of, and 6 weeks after 3 months of intensive residential treatment. An effect size of 1.22 on the PDS was found between baseline and follow-up. Effect sizes for secondary outcomes ranged from medium to large. The results suggest that DBT-PTSD has promise for reducing severe and chronic PTSD after CSA.