Anemia is one of the extra-articular findings of ankylosing spondylitis (AS), and anti-TNF therapy has been shown benefit in patients with anemia associated AS. In this study, we aimed to evaluate and compare the effects of biological and non-biological agents on hemoglobin levels in AS patients. One hundred consecutive patients who fulfilled ASAS criteria for AS were included in the study. Fifty-four of the patients treated with anti-TNF agents (20 patients treated with infliximab, 20 patients with adalimumab, and 14 patients with etanercept), and 46 patients treated with non-steroidal anti-inflammatory drugs and/or other disease modifying anti-rheumatic drugs. The C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), hemoglobin (HGB), hematocrit (HCT) counts, and BASDAI scores were compared before starting therapy and at 52 weeks. There was no statistically significant difference between patients about demographical data (age, sex) and disease age (p > 0.05 for all). Significant difference was determined between HGB, HCT, CRP, ESR, and BASDAI values before and after therapy (for infliximab p: 0.001; 0.000; 0.000; 0.000; 0.000, respectively, and for adalimumab p: 0.017; 0.03; 0.001; 0.002; 0.000, respectively). In etanercept group, there was no significant difference in HGB values, when compared with before starting therapy and at 52 weeks (p > 0.05). In the group of treated with non-biological agents, ESR values and BASDAİ scores showed distinctive improvement after 52 weeks of therapy, but was not a significant difference in hemoglobin and hematocrit values. Conclusion: Anti-TNF-alpha therapy with monoclonal antibodies (adalimumab and infliximab) did not only suppress disease activity but also provided a significant improvement in HGB levels. In the groups of treated with a TNF-alpha receptor antagonist (ETA) and non-biological agents, disease activity was suppressed, but there was not founded significant improvement in HGB levels after 52 weeks. Different outcomes of anti-TNF agents may be associated with their different effect mechanisms.