Objective: We aimed to investigate the effect of vitamin D deficiency as a risk factor for the development of gestational diabetes mellitus (GDM) among pregnant women without known risk factors. Materials and Methods: The study was conducted on pregnant women who had been under regular follow-up and had low risk for GDM development. The patients were divided into two groups according to the presence of GDM; GDM and no GDM (control) group. Body mass index (BMI), sociodemographic data including level of education and nutritional habits were recorded. Serum 25 (OH) vitamin D3 levels, hemoglobin, hematocrit, and mean corpuscular volume (MCV) values were measured. An oral glucose tolerance test was performed, between 24 and 28 weeks of pregnancy. Results: GDM ratio was calculated as 4.6%. The false positive rate of 50 g oral glucose load screening test was found to be 16.5%. The BMI levels of women diagnosed as having GDM and those with no GDM group at the beginningof the pregnancy period were calculated as 24.3±2.6 and 22.8±1.6 kg/m2 respectively, exhibiting a statistically significant difference between the two groups (p=0.001). Hemoglobin, hematocrit, and MCV values did not show a statistically significant difference between the two groups (p>0.05). The levels of 25 (OH) vitamin D3 of the study groups were found comparable in both groups (p=0.13). Conclusion: Plasma levels of vitamin D may not be a contributing factor for the development of GDM in women with a low risk for GDM. PRECIS: We evaluated the effect of vitamin D deficiency as a contributing factor for the development of gestational diabetes among pregnant women who have a low risk for gestational diabetes