Abstract Background: GDM affects both mother and baby during pregnancy and in the long term. Metformin was associated with a lower risk of neonatal hypoglycemia; however, met-formin may slightly increase the risk of prematurity. Aim of Study: The aim of the present study was to compare the safety and efficacy of metformin as an oral anti-diabetic drug with insulin as oral hypoglycemic drugs for management of gestational diabetes mellitus. Patients and Methods: 120 pregnant women with gesta-tional diabetes mellitus were included in this randomized controlled trial. Patients were randomly allocated into 2 groups as follows: Group I: Insulin group (n=64) and Group M: Metformin group (n=56). Follow-up was done every week by measuring fasting and post prandial blood glucose level. Maternal outcomes and neonatal outcomes were recorded. Results: There were statistically significant differences as regard mean fasting and post prandial blood glucose level and mean birth weight in insulin and metformin group. Also, increased CS rate between insulin and metformin group. There were statistically significant differences between insulin group and metformin sub-groups patients as regards birth weight, Apgar score and serum glucose level. Conclusion: We concluded that metformin is an effective and safe treatment option for women with GDM. Metformin is comparable with insulin in glycemic control, providing additional evidence for the use of metformin in GDM.