This study aimed to investigate the serum levels of interleukin-27 (IL-27) in patients with Takayasu arteritis (TA) and evaluate its role in determining disease activity. A total of 34 patients with TA (32 female, 2 male) and 34 healthy controls (32 female, 2 male) were enrolled. Patients with TA were divided into two groups: active and inactive, according to Kerr scores. Twenty-one patients were in active group (mean age; 27.1 ± 6.9 years, mean disease duration 7.2±2.8 years) and 13 patients were in inactive group (mean age; 32.7 ± 5.3 years, mean disease duration; 8.7±4.1 years). Serum IL-27 levels were determined by ELISA. The mean serum IL-27 levels were 19.7±4.8 pg/ml in healthy controls, 128.3±11.7 pg/ml in active group, and 45.2±9.5 pg/ml in inactive group. Serum IL-27 levels in patients with TA were significantly higher than in healthy controls (p<0.001). Serum IL-27 levels were significantly higher in active group compared with inactive group (p<0.001). Both in active and inactive groups, there was a statistically significant correlation between serum IL-27 and serum CRP and ESR (r=0.588, p <0.001, r=0.503, p <0.001 and r=0.474, p <0.01, r=0.446, p <0.01, respectively). Biomarker studies in TA are mainly focused on differentiating active stage from inactive stage. The serum level of IL-27 may be a potential biomarker, which is associated with disease activity in patients with TA.