Co-occurring posttraumatic stress disorder (PTSD) is prevalent in addiction treatment programs and a risk factor for negative outcomes. Although interventions have been developed to address substance use and PTSD, treatment options are needed that are effective, well tolerated by patients, and potentially integrated with existing program services. This paper describes a cognitive behavioral therapy (CBT) for PTSD that was adapted from a treatment for persons with severe mental illnesses and PTSD in community mental health settings. The new adaptation is for patients in community addiction treatment with co-occurring PTSD and substance use disorders. In this study, 5 community therapists delivered the CBT for PTSD. Outcome data are available on 11 patients who were assessed at baseline, post-CBT treatment, and at a 3-month follow-up post-treatment. Primary outcomes were substance use, PTSD severity, and retention, of which all were favorable for patients receiving the CBT for PTSD.