IMPORTANCE Diabetes in pregnancy is associated with a 2-times to 3-times higher rate of very preterm birth than in women without diabetes. Very preterm infants are at high risk of death and severe morbidity. The association of maternal diabetes with these risks is unclear. OBJECTIVE To determine the associations between maternal diabetes and in-hospital mortality, as well as neonatal morbidity in very preterm infants with a birth weight of less than 1500 g. DESIGN, SETTING, AND PARTICIPANTS This retrospective cohort study was conducted at 7 national networks in high-income countries that are part of the International Neonatal Network for Evaluating Outcomes in Neonates and used prospectively collected data on 76 360 very preterm, singleton infants without malformations born between January 1, 2007, and December 31, 2015, at 24 to 31 weeks' gestation with birth weights of less than 1500 g, 3280 (4.3%) of whom were born to diabetic mothers. EXPOSURES Any type of diabetes during pregnancy. MAIN OUTCOMES AND MEASURES The primary outcome was in-hospital mortality. The secondary outcomes were severe neonatal morbidities, including intraventricular hemorrhages of grade 3 to 4, cystic periventricular leukomalacia, retinopathy of prematurity needing treatment and bronchopulmonary dysplasia, and other morbidities, including respiratory distress, treated patent ductus arteriosus, and necrotizing enterocolitis. Odds ratios (ORs) with 95% confidence intervals were estimated, adjusted for potential confounders, and stratified by gestational age (GA), sex, and network. RESULTS The mean (SD) birth weight of offspring born to mothers with diabetes was significantly higher at 1081 (262) g than in offspring born to mothers without diabetes (mean [SD] birth weight, 1027  g). Of 76 360 infants, 25 962 (34%) and 33 598 (44%) were born before 28 weeks of gestation to mothers with and without diabetes, respectively. Mothers with diabetes were older and had more hypertensive disorders, antenatal steroid treatments, and deliveries by cesarean delivery than mothers without diabetes. Infants of mothers with diabetes were born at a later GA than infants of mothers without diabetes. In-hospital mortality (6.6% vs 8.3%) and the composite of mortality and severe morbidity (31.6% vs 40.6%) were lower in infants of mothers with diabetes. However, in adjusted analyses, no significant differences in in-hospital mortality (adjusted OR, 1.16 (95% CI, 0.97-1.39) or the composite of mortality and severe morbidity (adjusted OR, 0.99 (95% CI, 0.88-1.10) were observed. With few exceptions, outcomes of infants born to mothers with and without diabetes were similar regardless of infant sex, GA, or country of birth. CONCLUSIONS AND RELEVANCE In high-resource settings, maternal diabetes is not associated with an increased risk of in-hospital mortality or severe morbidity in very preterm infants with a birth weight of fewer than 1500 g.