Immune system-related factors are important in pathogenesis of multiple sclerosis. The CXC chemokine SDF-1α (CXCL12) is involved in the immune responses. Hence, the aim of this study was to investigate the association between serum levels of SDF-1α (CXCL12) and its gene polymorphisms at position +801 with multiple sclerosis. In this experimental study, blood samples were collected from 100 multiple sclerosis patients and 100 healthy controls on EDTA pre-coated tubes. DNA was extracted and DNA samples were analyzed for SDF-1α (CXCL12) polymorphisms using PCR-RLFP in patients and controls. The serum levels of SDF-1α (CXCL12) were measured by ELISA. Demographic data were also collected by a questionnaire which was designed specifically for this study. Our results showed a significant difference between the A/A, A/G, and G/G genotype and A and G alleles of polymorphisms at position +801 of SDF-1α (CXCL12). Our results also showed that serum levels of SDF-1α (CXCL12) were markedly higher in patients than healthy controls, but no association was observed between SDF-1α (CXCL12) polymorphism and its serum levels. The results of this study might suggest the serum levels of SDF-1α (CXCL12) and its polymorphism play an important role in pathogenesis of multiple sclerosis. It is also worth noting that these factors could probably use as pivotal biological markers in the diagnosis of MS.