Background: Single nucleotide polymorphisms (SNPs) in the Endoplasmic reticulum aminopeptidase (ERAP) 2 gene has been attributed in the pathogenesis of Ankylosing spondylitis (AS). Here we assessed the ERAP2 gene SNPs association with AS predisposition in Iranian patients and determined their effect on the inflammatory state of the patients.Methods: For genotyping of rs2548538, rs2287988, and rs17408150 SNPs using Real-time allelic discrimination approach, DNA was extracted from the whole blood of 250 AS patients and 250 healthy subjects. RNA of the peripheral blood mononuclear cells (PBMCs) was separated, cDNA was synthesized, and transcriptional levels of cytokines, including interleukin (IL)-17A, IL-23, IL-10, and transforming growth factor (TGF)-β were measured. Enzyme-linked immunosorbent assay (ELISA) was used to measure the serum concentration on the cytokines.Results: It was observed that three ERAP2 gene SNPs had no significant association with risk of AS in the total patients. Nonetheless, rs2287988 and rs17408150 SNPs showed statistically significant association with susceptibility to the disease in the Human leukocyte antigen (HLA)-B27 positive AS subjects. Transcriptional level and serum concentration of IL-17A and IL-23 were higher, while those of IL-10 were lower in both AS patients and HLA-B27 positive AS patients relative to controls. Nevertheless, ERAP2 gene SNPs in the HLA-B27 positive AS patients did not affect the transcriptional level and serum concentration of cytokines.Conclusions: ERAP2 gene rs2287988 and rs17408150 SNP are associated with susceptibility to AS, but they probably are not determining the levels of IL-17A, IL-23, and IL-10 in this disease.