Objective: To evaluate and compare serum leptin levels in pregnant women with gestational diabetes mellitus (GDM) and healthy glucose-tolerant controls, and to investigate the correlation of leptin with adiposity and insulin resistance markers. Methods: A comparative study involving 180 pregnant women (90 with GDM and 90 matched controls) conducted at a tertiary care teaching hospital. Participants were recruited at 24 to 28 gestational week range. Demographic and clinical data were recorded. Blood samples were analyzed for fasting glucose, insulin, and serum leptin levels. A 75-g oral glucose tolerance test (OGTT) was performed. Insulin resistance was calculated using the Homeostatic Model Assessment (HOMA-IR). Statistical analysis was performed using Student's t-test, Chi-square test, and Pearson’s correlation.Results: Women with GDM had a significantly higher pre-pregnancy BMI (26.4 ± 3.5 vs. 23.7 ± 3.0 kg/m², p < 0.001) and a greater family history of diabetes (51.1% vs. 23.3%, p < 0.001) compared to controls. As expected, the GDM group exhibited higher fasting glucose, 1-h and 2-h OGTT values, fasting insulin, and HOMA-IR (all p < 0.001). Serum leptin levels were markedly elevated in the GDM group (38.4 ± 11.2 ng/mL) compared to the control group (24.7 ± 8.6 ng/mL, p < 0.001). Correlation analysis revealed significant positive associations between serum leptin and pre-pregnancy BMI (r = 0.56, p < 0.001), fasting insulin (r = 0.49, p < 0.001), and HOMA-IR (r = 0.52, p < 0.001).Conclusion: Serum leptin levels are significantly elevated in women with GDM and are strongly correlated with increased pre-pregnancy BMI and insulin resistance. This suggests that leptin dysregulation may play an important role in the pathophysiology of GDM, potentially linking adipose tissue dysfunction to impaired glucose metabolism in pregnancy.