Background: Obsessive-Compulsive Disorder (OCD) is a serious neuropsychiatric disorder. The clinical prominence of the OCD symptoms dimensions and Brain-Derived Neurotrophic Factor (BDNF) Val66Met polymorphism are of significant importance. Objectives: The present study aimed to investigate the symptom dimensions and BDNF val66Met polymorphism genotype in Iranian patients with OCD. Materials and Methods: A total of 83 patients diagnosed with OCD according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM5) criteria, and 83 matched controls were included this case-control study. The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) was used to investigate symptom dimensions. In addition, BDNF val66Met polymorphism was genotyped using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCRRFLP) method. Results: The obtained data indicated that the most prevalent obsession was contamination (62.6%) and the most prevalent compulsion was cleanliness (69.8%). Furthermore, there was a significant relationship between the genotypes of BDNF val66Met polymorphism in OCD (P<0.01). Besides, carrying the” T” allele confers increased the risk for the presence of OCD [χ2=4.7, P=0.003; OR (95%) 1.93 (1.24-2.99)]. Conclusion: The symptoms dimensions of OCD in the Iranian sample were similar to other populations. Moreover, the findings suggested an association between BDNF val66Met polymorphism genotype and OCD in the explored Iranian sample. The inheritance hypothesis for the TT genotype was the recessive model.