Introduction: PCOS is a common condition that increases the risk of gestational diabetes mellitus (GDM) due to insulin resistance. The purpose of this study is to evaluate the relationship between PCOS and Gestational Diabetes Mellitus. Aim of the study: The aim of the study was to evaluate the relationship between Polycystic Ovary Syndrome (PCOS) and the development of Gestational Diabetes Mellitus (GDM) in pregnancy. Methods: This comparative cross-sectional study was conducted in the Department of Obstetrics and Gynecology at Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh, from June 2015 to May 2016. It involved 100 pregnant women, 50 with PCOS and 50 without, who underwent fasting glucose, 2-hour OGTT, and HOMA-IR tests. Data on gestational diabetes and pregnancy complications were collected and analyzed using SPSS version 22.0. Result: The study revealed that the PCOS group was older (29.4 ± 4.1 years) compared to the Non-PCOS group (27.2 ± 5.0 years), with a higher incidence of GDM (26.00% vs. 10.00%). Pregnancy complications like preterm birth were more common in the Non-PCOS group (24.00%), while GDM occurred more often in the PCOS group (26.00%). Additionally, the PCOS group had higher fasting and 2-hour OGTT glucose levels and showed greater insulin resistance (3.5 ± 1.2 vs. 2.3 ± 0.9). Conclusion: This study confirms that women with Polycystic Ovary Syndrome (PCOS) have an increased risk of Gestational Diabetes Mellitus (GDM) and exhibit impaired glucose metabolism, underscoring the importance of close monitoring during pregnancy.