Although childhood sexual abuse and childhood physical abuse (CSA and CPA) have severe psychopathological consequences, there is little evidence supporting psychotherapeutic interventions for adolescents who have experienced CSA or CPA. To provide a treatment tailored to the specific needs of adolescents suffering from abuse-related posttraumatic stress disorder (PTSD), we modified Cognitive Processing Therapy (CPT) by adding new treatment modules and changing the therapy setting. To evaluate the feasibility and efficacy of Developmentally Adapted CPT (D-CPT), we treated 12 adolescents suffering from PTSD secondary to CSA or CPA. Patients were assessed prior to treatment (t0), post-treatment (t1), and 6 weeks after treatment (t2). Assessments included the Clinician-Administered PTSD Scale (CAPS), the UCLA PTSD Index (UCLA), the Children's Depression Inventory (CDI), the Adolescent Dissociative Experiences Scale (A-DES), and the Borderline Symptom List (BSL-23). MANOVAs revealed that posttraumatic stress measurements and associated symptom measurements significantly differed across time points. When comparing t0 with t2, Cohen's d was large with respect to the CAPS scores (d = 1.45, p < .001) and the UCLA scores (d = 1.91, p < .001). Cohen's d had a medium magnitude with respect to the CDI scores (d = .78, p < .001), the A-DES scores (d = 0.64, p < .05), and the BSL-23 scores (d = 0.74, p < .01). D-CPT has the potential to reduce PTSD symptoms and comorbid psychopathology in adolescents with histories of CSA or CPA.