Objective: To evaluate neonatal respiratory morbidity in infants born late-preterm to mothers with or without gestational diabetes mellitus (GDM). Methods: Analysis of a population-based cohort of all live-born singletons, born at 34 0/7 to 36 6/7 weeks to mothers with and without GDM, focusing on transient tachypnea of the newborn (TTN) and respiratory distress syndrome (RDS).Results: The study group comprised 363 (4.7%) singletons born to mothers with GDM and the controls were 7400 born to mothers without GDM. Mothers with GDM were older (31.4 ± 5.1 versus 29.5 ± 5.1 years, p < 0.001) and were more likely to be hypertensive (OR 1.5, 95% CI 1.1–2.1). Neonates of GDM mothers were heavier at birth (2769 ± 539 versus 2636 ± 473 g, p < 0.001). We found a similar incidence of RDS and TTN in both groups. The multiple regression analysis showed cesarean delivery and lower gestational age were independently associated with RDS and TTN.Conclusion: GDM, per se, is not a major contributor to RDS in late pre-term infants. Rather, the combination of prematurity and cesarean birth act independently to increase the risk of respiratory morbidity.