AIM: To assess role of vitamin D-calcium supplementation on the metabolic profile and oxidative stress in women with Gestational Diabetes Mellitus (GDM) controlled on diet. METHODS: A randomized controlled trial was conducted at a tertiary care teaching hospital. Seventy women diagnosed as GDM at 24-28 weeks of gestation, controlled on a diabetic diet, were randomized to receive either vitamin D 1000 IU and calcium 1000 mg (group A, n = 34) or vitamin D 250 IU and calcium 500 mg (group B, n = 36) daily for 6 weeks. Levels of serum 25-hydroxy vitamin D, fasting plasma glucose (FPG), serum insulin, fasting lipid profile and total glutathione (GSH) were analyzed both prior to and after supplementation. Means, standard deviations and mean change were computed. Paired and independent t-tests were used to determine statistical significance between the two groups. RESULTS: Women in group A showed a significant reduction in FPG level (P-value = 0.007), fasting serum insulin level (P-value = 0.000), LDL (P-value = 0.000), total cholesterol levels (P-value = 0.000) and increase in HDL levels (P-value = 0.000). Group B had a significant fall only in FPG after 6 weeks supplementation. A significant change in total glutathione level (P-value = 0.000) was observed in both groups. CONCLUSION: Vitamin D and calcium supplementation at a dose of 1000 IU and 1000 mg, respectively, has a beneficial role in glucose metabolism, lipid metabolism and oxidative stress in GDM.