Objective: Gestational diabetes mellitus (GDM) is a metabolic disorder during pregnancy leading to acute and chronic complications in both mother and newborn. The pathogenesis of GDM has not been fully understood, However, since the disease shares risk factors with type 2 diabetes mellitus (T2DM), a relationship between these two disease states is plausible. The recently discovered peptide irisin has been hypothesized to be a regulator of body metabolism. However, studies ended up with controversial results. In the present study, we aimed to investigate the relationship between irisin levels and gestational diabetes mellitus and the possible benefits of the metabolic profile. Materials and methods: We performed a cross-sectional analysis of circulating levels of irisin in 100 pregnant women similar for age and body mass index and the groups included 50 gestational diabetic patients and 50 healthy pregnant volunteers. Serum irisin levels were measured by ELISA kit. Results: Mean age and body mass index levels were similar in both groups. Median HbA1c, fasting blood glucose, Glucose 1 h, Glucose 2 h and fasting insülin levels were higher in with gestational diabetic patients compared to the control group. In gestational diabetic group, the median irisin level was lower than in the control group. Conclusion: Serum irisin levels were lower in gestational diabetic patients. Further investigations are needed to explore the underlying biological effects of irisin on pregnant women.