Background: Insulin therapy is required in gestational diabetes mellitus (GDM) when glycaemic targets are not achieved through lifestyle modification and rapid acting insulin analogues such as regular aspart insulin have been developed to provide more physiological postprandial and fasting glucose control than regular human insulin. This study aimed to compare glycemic control, including fasting, postprandial and glycated haemoglobin parameters, between regular aspart insulin and regular human insulin in women with gestational diabetes mellitus. Methods: This randomized controlled trial was conducted in the outpatient department of Obstetrics and Gynaecology, BIRDEM General Hospital, Dhaka, from October 2023 to January 2025, among 102 pregnant women with GDM diagnosed after 24 weeks of gestation. Participants were randomly allocated to regular aspart insulin (Group I, n=54) or regular human insulin (Group II, n=48); 49 and 46 women respectively completed follow up at 28, 32 and 36 weeks of gestation and after delivery. Fasting blood sugar, postprandial glucose two hours after breakfast, lunch and dinner and HbA1c were compared using SPSS version 26, with p<0.05 considered significant. Results: Mean age of participants was 29.2 ± 4.6 years and 63.16% were obese before pregnancy. Fasting glucose was significantly lower in Group I at every assessment point (p<0.0001). Postprandial glucose values were also significantly higher in Group II at 28 weeks (p<0.05 for all three postprandial readings), but these differences attenuated by 32 and 36 weeks and after delivery. HbA1c was comparable between groups at 28 weeks (6.1 ± 1.0 versus 6.4 ± 1.4, p=0.327) and 36 weeks (5.8 ± 1.0 versus 5.9 ± 1.4, p=0.697). Conclusion: Regular aspart insulin provided superior fasting glycaemic control throughout pregnancy and more favourable early postprandial control than regular human insulin, while overall glycated haemoglobin remained comparable, supporting its use as an effective glycaemic management option in gestational diabetes mellitus.