Background & aim: Considering that veterans as the most important target groups for health care facilities, and social psychology is taken into account, the aim of this study was to evaluate the efficacy of psychological debriefing and group behavioral interventions in reduction of posttraumatic stress disorder on veterans of Yasuj city. Methods: In this clinical-trial study, 20 patients were selected among veterans with post-traumatic stress disorder, and then randomly assigned to experimental and control groups. The Mississippi Scale for Posttraumatic Stress Disorder (M-PTSD) was administered by Research Tool to both groups before training. One session for psychological debriefing and 6-week sessions for behavioral interventions at 90-minute was conducted only for the experimental group. After a period of three months, the two groups were assessed to determine the effect of training. Data were analyzed using multivariate analysis of covariance. Results: The mean and standard deviation of posttraumatic stress disorder in patients after the intervention and control groups were 103/6±11/27 and 112±8/68, respectively. There was no significant difference between them (p<0.05). Conclusions: Treatment method of psychological and behavioral interventions can be effective in the treatment of chronic post-traumatic stress disorder. This therapeutic effect to be maintained even after three months. Key words: Post Traumatic Stress Disorder, Psychological Debriefing, Behavioral interventions