Background: Obsessive-compulsive disorder (OCD) is  a mental disorder in which a person has certain thoughts repeatedly or feels the need to perform certain routines repeatedly to an extent that generates distress or impairs general functioning, affects approximately 2-3% of the world population. The first-line treatments are selective serotonin reuptake inhibitors and cognitive behavioral therapy. Despite that, approximately 40- 60% of patients remain treatment refractive. Objective: Evaluating the efficacy of low frequency repetitive transcranial magnetic stimulation (rTMS) applied over the supplementary motor area (SMA) on both sides as an adjunctive treatment for OCD. Methods: Twenty-four patients with OCD were randomly assigned to 2 weeks either active LF (1 Hz, n=12) with parameters (25-minute trains, 1,500 pulses/day each side at 100% of the resting motor threshold RMT, 5 sessions/week) or sham (n=12) (same LF parameters with coil tilting). OCD symptoms were assessed using: Yale-Brown Obsessive Compulsive Scale (Y-BOCS) before and immediately after sessions. Results: A repeated-measures analysis of variance (ANOVA) revealed a significant reduction in Y-BOCS scores in the active groups compared with the sham group after 2 weeks. There were no reports of serious adverse effects following the active or sham rTMS treatments. Conclusion: LF rTMS over the supplementary motor area (SMA) on both sides appeared to be superior to sham rTMS for relieving OCD symptoms in patients with OCD. Further trials with larger sample sizes should be conducted to confirm the present findings.