Background: An autoimmune and inflammatory illness called rheumatoid arthritis (RA) occurs when your immune system mistakenly attacks normal cells in your body. Interleukin-35 is a brand-new cytokine that belongs to the immunosuppressive and anti-inflammatory IL-12 family. β -herpesvirus that produces inflammation and stays dormant in its host for life is the human cytomegalovirus. Human herpesvirus (HCMV) has been at the core of several RA-related theories. Objective: The current study looked at the association between RA and serum IL-35 levels as well as the association between RA and CMV. Patients and methods: Blood samples were taken in the Baghdad Teaching Hospital and Typical Rheumatology Unit from January 2022 to Mars 2022 for the current study, which comprised 70 Iraqi patients with RA illnesses and 22 Iraqi controls. ELISA was utilized to measure the biomarkers in this investigation, including the levels of IL-35 and anti-CMV lgG. Results: In comparison to control group, RA patients had increased levels of IL-35, but there was no statistical significant difference between the two groups. Because all participants in our research had anti-CMV IgG, it was determined that both sick and healthy individuals had previously been infected with the virus. Conclusion: Our results showed the role of IL-35 as a cytokine against inflammation and contributed to the control of RA pathogenesis, as well as the association between IL-35 and HCMV and whether the illness is active or not.