The purpose of our study was to measure epicardial adipose tissue (EAT) thickness as a novel indicator of atherosclerosis and cardiovascular risk factor in ankylosing spondylitis (AS) patients and to show the relationship with clinical parameters and inflammatory markers. Forty AS patients (42.75 ± 12.43 years) and 40 healthy individuals with no cardiovascular risk factor as the control group (43.02 ± 14.78 years) were included in the study. Carotid intima-media thickness (CIMT) and EAT thickness were measured in AS patients and the control group. Total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, glucose, erythrocyte sedimentation rate, urea, and blood pressure were investigated in both groups. In addition, the Bath Ankylosing Spondylitis Functional Index (BASFI) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were used to evaluate the association between clinical findings and CIMT and EAT in the patient group. CIMT and EAT thickness were higher in the AS patients compared to the control group. CIMT was 0.76 ± 0.19 and 0.57 ± 0.12 mm (p < 0.001) and EAT thickness was 4.35 ± 1.56 and 3.03 ± 0.94 mm (p < 0.001) in the AS and control groups, respectively. A correlation was determined between EAT thickness and CIMT. Triglyceride level, patient age, blood pressure, and duration of disease were correlated with both CIMT and EAT thickness. Increased CIMT and EAT thickness in AS patients compared to the control group shows a risk for subclinical atherosclerosis and cardiovascular disease.