Background: Gestational diabetes mellitus is a common metabolic complication of pregnancy and is associated with significant maternal and neonatal morbidity. The rising prevalence of gestational diabetes, particularly in low- and middle-income countries, poses increasing challenges for obstetric and neonatal care. Maternal hyperglycemia alters intrauterine metabolic conditions, potentially leading to adverse delivery outcomes and early neonatal complications. Objective: To evaluate the impact of gestational diabetes mellitus on mode of delivery, maternal complications and early neonatal outcomes in a tertiary care hospital setting. Methods: This prospective observational study was conducted in the Department of Obstetrics and Gynecology, Rangpur Medical College and Hospital, Bangladesh, from January to December 2025. A total of 150 pregnant women were enrolled, including 75 with gestational diabetes mellitus and 75 without gestational diabetes. Maternal socio-demographic characteristics, obstetric outcomes and early neonatal outcomes were recorded. Data were analyzed using descriptive statistics and chi-square tests. Results: Women with gestational diabetes had higher rates of caesarean section (52.0% vs. 32.0%), pregnancy-induced hypertension (18.7% vs. 8.0%), preterm delivery (21.3% vs. 9.3%) and polyhydramnios (10.7% vs. 2.7%). Neonates born to mothers with gestational diabetes showed increased macrosomia (22.7% vs. 8.0%), neonatal hypoglycemia (18.7% vs. 4.0%) and neonatal intensive care unit admission (24.0% vs. 9.3%). Conclusion: Gestational diabetes mellitus significantly increases the risk of adverse maternal and early neonatal outcomes. Early detection and comprehensive management strategies are essential to reduce associated morbidity.