Interleukin (IL) -22 is a novel mediator of a member of IL-10 family cytokines that is produced by many different types of lymphocytes including both those of innate and adaptive immune system. This cytokine has potent proliferative and inflammatory effects on different cell lines. Recently, accumulated data has indicated that IL-22 plays an important role in the pathogenesis of rheumatoid arthritis (RA). We aimed to investigate the levels of IL-22 and its association with demographic, clinical data as well as serological markers in RA. IL-22 serum levels were measured in 45 newly diagnosed RA patients without any treatment and 45 healthy individuals as control by a manual Enzyme linked immunosorbent assay (ELISA). Correlations of IL-22 serum levels were sought with demographic, clinical data and serological parameters. IL-22 levels were significantly elevated in serum of RA patients (median= 86.89ng/ml and range = 896) compared to serum of healthy control (median=75.36ng/ml and range=459), p=.022. The IL-22 levels were correlated positively with C-reactive protein (CRP), anti-cyclic citrullinated peptide (ACCP) antibodies in RA patients. Significant higher levels of serum IL-22 in RA patients compare with those in healthy control. Highly significant association between serum levels of IL-22 and the serological markers (CRP and ACCP antibodies) in the diagnosis of RA suggest the potential levels of IL-22 as a valuable biomarker for the evaluation of disease severity in RA patients. Keywords: Anti-cyclic citrullinated peptide antibody, C-reactive protein, Interleukin-22, rheumatoid arthritis, rheumatoid factor.