Background Rheumatoid arthritis (RA) is one of common autoimmune disorder globally affected 1% of population characterized by irregular cytokine production. microRNAs can influence the cytokine production that is associated with autoimmunity. Biomarkers found in local and systemic inflammation may give the solution for accurately diagnosing and treating arthritis. Objective: to evaluate TNF-α levels in synovial fluid and serum with serum miRNA-155 expression as prognostic markers in RA individuals. Methodology: 80 RA patients were attended to Al-Saddar Medical City Rheumatology Unit in the Najaf Governorate and 40 healthy as control group were selected for case-control study. The mean patients' age was 50.6±16.5 and 42.5±9.24 years for healthy group. These patients were diagnosed by specialized physicians and given a diagnosis of rheumatoid arthritis then classified into mild (stage1 and 2) and aggressive stages (stage 3 and 4). Three ml of venous blood were taken from all participant from which 2 ml were placed in gel tube for serum separation to measuring RF and ACCP as confirmative diagnosis, the other 1ml was placed in Eppendorf tube with Triazole and immediately stored at -20 C◦ for miRNA -155 evaluation by RT-PCR, Knee synovial fluid was separated from Knee effusion of both RA patients and patients suffering from knee trauma only as control group. TNF-α was measured in serum and S.Fluid by ELISA assay. Results: that RA patients between the ages 45 - 67 years had a greater incidence and severity of the illness. TNF-α levels were substantially greater in patients with Aggressive-stage disease than in patients with mild-stage. According to ROC analysis appropriate cut-off value of miRNA-155 was 1.66, which had 0.944 % sensitivity, 0.889% specificity, AUC= 0.972, at P=0.000***. while the appropriate cut-off value of TNF-α appeared with high validity as prognostic factors in both serum and S. Fluid ( 87 % sensitivity, 97% specificity, AUC 0.992 in serum and 83.3% sensitivity, 86.7% specificity, AUC 0.915 in synovial Fluid. Conclusion: By using ROC analysis, it was possible to achieve good diagnosis accuracy for TNF-α levels in both serum and synovial fluid, as well as more sensitive and accurate discrimination of RA disease. TGF-β1 and miRNA-155 blood levels may help patients to avoid discomfort and stress instead of employing synovial fluid separation as a diagnosis for excellent prognosis in RA illness.