Aim: Gestational diabetes mellitus (GDM) is an important disease worldwide and its incidence is rising with increasing maternal age and obesity. The aim of this study is to investigate the prevalence of GDM in accordance with International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria by obtaining data from a single center in Kayseri. Methods: All pregnant women between the ages of 18 and 45 who were referred to the clinic for routine pregnancy follow-up visits between January 2018-2019 at Kayseri City Hospital's Gynecology and Obstetrics Department were included in this study. Their records were obtained from the hospital registry and retrospectively examined. A single stage 75g oral glucose tolerance test (OGTT) was performed to all patients and IADPSG criteria were used for diagnosis. Results: 2652 pregnant women were included in this study and screened for GDM with a single-step 75-g OGTT. The mean age of all pregnant women was 26.42 (22-31) years. The mean gravid, parity and gestational weeks at the time of testing were 3 (range 1-5), 3 (range 1-4), 26 (range 24-28), respectively. The prevalence of GDM, detected in 424 of 2652 patients, was 16% (424/2652). Conclusion: The prevalence of GDM among pregnant women who were referred to our clinic for routine pregnancy follow-up was 16% according to the IADPSG criteria, as determined with a single-step 75-g OGTT.