Objective: The aim of this study was to investigate the effectiveness of cognitive processing therapy in emotional representation and reduction of self-destructive behaviors in addicts with PTSD. Method: This study used an experimental research design along with pretest-posttest control group. The statistical population of the present study included all addicts in the Urmia Hayat Addiction Treatment Clinic in 2016. After implementing Mississippi Scale for Combat-Related Posttraumatic Stress Disorder on 170 members of them, 40 participants were selected and randomly assigned to two groups. Then, Impact of Event Scale - Revised (IES-R) and Self-destructive Behavior Questionnaire were administered pretests. Participants in the experimental group received 12 sessions of cognitive processing therapy. The test was conducted. Data were analyzed using multivariate analysis of covariance. Thereafter, the posttest was conducted. Results: The results of this study showed that there is a significant difference between post-test and follow-up test in the mean scores of negative emotional representations and self-destructive behaviors. Conclusion: The results of this study address the need for implementing a trauma-focused therapy like Cognitive Processing Therapy in order to treat the drug addicts who have been faced with post-traumatic stress.