Obsessive-compulsive disorder (OCD) is a chronic neuropsychiatric disorder with complex genetic inheritance. Findings suggest a role for brain-derived neurotrophic factor (BDNF) in OCD, but reports are limited. Here we studied the association of BDNF polymorphisms rs6265 and rs2883187 with OCD and its clinical characteristics in Iranian patients as well as the fluvoxamine-treatment outcome of OCD patients. Iranian OCD patients who were diagnosed according to DSM-IV-TR entered the study. DNAs were extracted from blood samples and were genotyped by means of PCR-RFLP. A total of 200 OCD cases and 225 controls for rs6265 and 219 cases and 224 controls for rs2883187 were studied in the genetic association analysis. Pharmacotherapy was defined as 12 weeks treatment with fluvoxamine (daily dose: 150-300 mg), and patients were classified into 3 groups (responders, nonresponders, and refractory) based on the reduction in their Y-BOCS severity scores. Data of 94 patients for rs6265 and 106 patients for rs2883187 was analyzed to evaluate the association of these single nucleotide polymorphism (SNPs) with treatment response. A significant association was detected between the BDNF polymorphism rs2883187 and OCD (p = .00). The other BDNF polymorphism, rs6265, was not associated with OCD, but a weak association with the cleaning-contamination subtype was detected (p = .038). No association was detected between BDNF SNPs and sex, age of onset, and family history. None of the studied BDNF SNPs or their haplotypes were associated with fluvoxamine treatment response. Results propose BDNF SNP, rs2883187, as a candidate genetic factor in OCD but not in OCD treatment response with fluvoxamine. (PsycInfo Database Record (c) 2020 APA, all rights reserved).