Objective: To determine frequency of gestational diabetes and its associated risk factors among pregnant women. Methodology: This descriptive cross sectional study was conducted in Department of Obstetrics & Gynecology, Pakistan Institute of Medical Sciences, Islamabad, Pakistan from April 2017-September 2017. A total of 380 patients were recruited using simple random sampling. Patients underwent detailed history and oral glucose tolerance test (OGTT) using American Diabetes Association guidelines. OGTT was considered normal with blood sugar fasting (BSF) < 95mg/dl, after 1 hour < 180mg/d1, after 2 hour < 155mg/dl and after 3 hours < 140mg/dl. SPSS version 22.0 was used for data analysis. Results: Out of 380 patients, 270(71%) were in age group 22-32 years while 110(29%) were in 33-45 years age group. Mean gestational age was 29.9 +/- 8.7 weeks. Frequency of gestational diabetes mellitus was 24%. A significant association between GDM and age (p=0.01), education (p=0.03), Parity (p=0.00), time interval between pregnancies (p=0.01) and gravidity (p=0.00) was found. Conclusion: High frequency of gestation diabetes mellitus was found. It was strongly associated age, educational level, parity, gravidity and time interval between pregnancies. (Rawal Med J201:43:459-461).