Objective: There are different pathophysiological mechanisms for obsessive- compulsive disorder (OCD) as suggested by the serotonergic, dopaminergic, and glutamatergic hypotheses. The present study aimed at comparing the efficacy and safety of saffron (stigma of Crocus sativus) and fluvoxamine in the treatment of mild to moderate obsessive- compulsive disorder. Method: In this study, 50 males and females, aged 18 to 60 years, with mild to moderate OCD, participated. The patients were randomly assigned to receive either saffron (30 mg/day, 15 mg twice a day) or fluvoxamine (100 mg/day) for 10 weeks. Using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Adverse Event Checklist, we assessed the patients at baseline, and at the second, fourth, sixth, eighth, and tenth week. Finally, the data were analyzed using general linear repeated measures. Results: In this study, 46 patients completed the trial. General linear repeated measures demonstrated no significant effect for time-treatment interaction on the Y-BOCS total scores [F (2.42, 106.87) = 0.70, P = 0.52], obsession Y-BOCS subscale scores [F (2.47, 108.87) = 0.77, p = 0.49], and compulsion Y-BOCS subscale scores [F (2.18, 96.06) = 0.25, P = 0.79]. Frequency of adverse events was not significantly different between the 2 groups. Conclusion: Our findings suggest that saffron is as effective as fluvoxamine in the treatment of patients with mild to moderate OCD.