Backgrund & Objectives: Obsessive–, Compulsive Disorder (OCD) is a common psychiatric ailment. Although Pharmacotherapy combined with psychotherapy (cognitive–, behavioral therapy, exposure and response prevention therapy) are the mainstays of OCD treatment, still a lot of patients do not respond adequately to these treatments. One reason is that the above mentioned treatments do not focus on emotions, interpersonal relationships and intimacy that play important role in psychiatric ailments. The role of emotions in psychiatric ailments has been noticed by researchers in previous studies. Guilt feeling is a very important emotion that has always been considered in the etiology and treatment of OCD. Psychodrama is a form of group psychotherapy which emphasizes on emotions, catharsis and interpersonal relationships. Previous studies have shown the effectiveness of psychodrama in improving psychiatric conditions such as anxiety and mood disorders as well as excoriation (skin picking) as a comorbid disorder with OCD. The purpose of this study was to investigate the effectiveness of psychodrama on improvement of feeling of Guilt in patients with obsessive–, compulsive disorder. Methods: This research was implemented via a quasi–, experimental method with pretest–, posttest design with contro group. Statistical population were all OCD patients referred to NikAvin psychology and counseling clinic in Isfahan, Iran. 24 OCD patients (16 females and eight males) who were diagnosed with OCD by a psychiatrist and according to the Maudsley Obsessive–, Compulsive Inventory (MOCI), were selected by convenience sampling and randomly divided into equal–, sized experimental and control groups (n=12). Data were collected before and after the intervention using Guilt Inventory (Asgari, 2009) extracted from revised version of Eysenck Personality Inventory (1985). The experimental group attended in 12 group sessions of psychodrama therapy. Three sessions were held each week for four weeks. The content of the treatment sessions in this study was created and designed by the first author of the article (Shirani) in 2020 in accordance with Moreno's therapeutic techniques and based on the manual of Karp et al. (2005). To evaluate the validity of the psychodrama package, the content validity index (CVI) and the opinion of five university experts were used and its value was 0. 8 for all sessions, which indicates the desired CVI according to the cutting points of this index for the package. To analyze the data from descriptive statistics indicators (mean and standard deviation) and from inferential statistics including statistical method of analysis of covariance was used in SPSS software version 23 at a significance level of p<0. 05. Results: The results showed that after eliminating the effect of pretest, a significant difference was observed in the variable score of feeling of Guilt in the posttest between the experimental group and the control group (p<0. 001). Conclusion: It is cocluded that psychodrama therapy has a significant effect on reducing the feeling of Guilt in OCD patients. Therefore, it is recommended that this treatment, along with medication or exposure and response prevention therapy be provided to help OCD patients.