OBJECTIVES: To compare the efficacy and safety of tocilizumab with those of abatacept in patients with active rheumatoid arthritis not responding to anti-tumor necrosis factor therapy. METHODS: A prospective, open-label study was carried out on adult females with moderate-to-severe rheumatoid arthritis. Patients were randomly assigned to receive either intravenous tocilizumab or abatacept treatment. History taking, clinical examination, and laboratory evaluation were done at baseline and during a 24-week period of follow-up. Disease activity was calculated using the DAS28-ESR score. The incidence of accompanying adverse events was evaluated and all statistical analyses were performed by InStat. RESULTS: One hundred thirty-two patients were enrolled and classified randomly into the tocilizumab (n = 68) and abatacept (n = 64) groups. By week 24, the mean DAS28-ESR was significantly reduced in both groups (P < 0.0001) in association with significant reductions in CRP, ESR, and HAQ scores. No significant difference in the incidence rate of adverse effects appeared between both study groups. However, there were marked declines in the hemoglobin levels (P = 0.003) and neutrophil count (P = 0.002) together with significant elevations in systolic blood pressure (P = 0.002), liver enzymes (P = 0.001), total cholesterol (P = 0.001), and high-density lipoproteins (P = 0.002) in the tocilizumab group compared with the abatacept group. CONCLUSION: Both intravenous abatacept and tocilizumab significantly decreased the disease activity and improved the physical function in rheumatoid arthritis patients who failed to respond to anti-tumor necrosis factor therapy. Although the efficacy of both drugs was similar, abatacept showed a more promising short-term safety profile since it was associated with less adverse effects and better laboratory outcomes.