Purpose: The aim of the study was to evaluate the frequency of anemia in patients with ankylosing spondylitis (AS) and to observe the change of anemia with biological disease-modifying drug (bDMARDs) treatment.,Materials and Methods: 137 patients with AS were included in the study with follow-up in the Physical Medicine and rehabilitation outpatient clinic. Patients' hemoglobin (HGB), ferritin, iron, iron binding capacity, erythrocyte volume (MCV), hematocrit (HCT), erythrocyte sedimentation rate (ESH)), C-reactive protein (CRP) levels were recorded by examining the hospital data recording system. The data obtained before and 1 year after the treatment were compared and anemia evaluations of the patients were made. The increase in hemoglobin values in patients using adalimumab and golimumab was compared.,Results: Anemia was detected in 56 (56.5%) of 99 patients included in the study. Iron deficiency anemia was found in 49 (49.4%) patients, and anemia of chronic disease was found in 7 (7%) patients. In all patients examined at the 52nd week of bDMARDs treatment, an increase in erythrocyte counts and HGB levels was detected, along with a decrease in ESR and CRP values. A significant increase in HGB levels was observed in all patients. When the increase in hemoglobin levels was compared between adalimumab and golimumab, no significant difference was found.,Conclusion: With bDMARDs treatment, which is effective in controlling the disease, an improvement can be seen in the anemia levels of AS patients.