Objective In Germany, patients with posttraumatic stress disorder (PTSD) related to childhood sexual abuse (CSA) often receive inpatient treatment. However, data on utilization and costs of mental health care as well as on the impact of trauma-focused treatment are missing. Methods Within the context of a randomized controlled trial mental health service utilization was assessed in female patients with PTSD related to CSA. Data on psychiatric-psychotherapeutic inpatient and outpatient treatment and psychotropic medication was obtained for the year before and after inpatient DBT-PTSD. Results The mean total costs of utilization of psychiatric-psychotherapeutic care and use of psychotropics were (sic) 18.100 per patient in the year before and (sic) 7.233 in the year after DBT-PTSD. The significant cost decrease was due to large reductions in inpatient treatment days (on average 57 days before and 14 days after DBT-PTSD), while outpatient treatment and psychotropic medication remained unchanged. Conclusion PTSD related to CSA is associated with high utilization and costs of mental health care. The results suggest that DBT-PTSD might contribute to reducing the mental health care costs.