Analog triptorelin is one of the effective agonists for the treatment of reproductive disorders, particularly prostate cancer. Due to results of previous studies, we hypothesized that obsessive-compulsive disorder (OCD can be effectively treated with the long-term administration of a gonadotropin-releasing hormone (GnRH) analog, namely triptorelin. The aim of this study was to evaluate the effectiveness of triptorelin injection in clients with OCD. This randomized single-blind clinical trial was performed on 30 clients with OCD who had a Yale-Brown score of > 17 after 8 weeks of treatment. The participants were randomly assigned into two groups of triptorelin and placebo. The clients in the intervention group were treated with Selective serotonin reuptake inhibitors (SSRIs), including fluoxetine, in addition to triptorelin three times a month for at least 8 weeks. Clients in the control group received injection of distilled water as placebo three times in addition to the routine treatment. The outcome was evaluated by Yale-Brown OCD scale (Y-BOCS) at the baseline, as well as 4, 8, and, 20 weeks after the end of the treatment. The mean scores of Y-BOCS in the intervention and control groups was 30.5 ±67.6 and 30.5 ±67.6, respectively, before intervention, indicating no significant difference between the two groups (P = 0.0.8). The comparison of Y-BOCS scores after the intervention showed a significant difference between the two groups in the scores 4 (P = 0.01), 8 (P < 0.005), and 20 (P < 0.005) weeks after the treatment. With regards to the side effects of the medicine, 6.7% (n = 1) of the clients in the control group developed headache and 66.7% (n = 10) had late period in intervention group. The results revealed a significant difference between the two groups in terms of side effects (P < 0.005). The results of this study showed triptorelin decreased the symptoms of OCD. The effectiveness of triptorelin in the treatment of symptoms in clients with OCD was confirmed in our study. However, due to the limited research addressing this domain, future studies are suggested to clarify this conclusion.