OBJECTIVE: To examine the association between the mode of delivery and the risk of offspring obesity by age 21 years using a large community-based birth cohort study in Australia. METHODS: We followed-up a subsample of 2,625 offspring for whom we had measured physical assessments, including height and weight at 21 years and hospital-recorded mode of delivery, in the Mater Hospital in Brisbane, Australia, between 1981 and 1983. Body mass index (BMI) and waist circumference were measured at 21 years. Multivariable regression analysis was used to examine the independent associations of mode of delivery with offspring BMI and waist circumference. RESULTS: In the cohort, 12.1% were born by cesarean delivery. Maternal and birth factors independently associated with the mode of delivery were age, overweight and obesity status, smoking status during pregnancy, hypertensive disorder during pregnancy, and neonatal low birth weight. By 21 years, 21.5% of offspring were overweight and 12.4% were obese. Offspring overweight and obesity status, as well as BMI and waist circumference, were not associated with the mode of delivery. CONCLUSIONS: Findings of this study do not support the idea that cesarean delivery has increased the risk of long-term offspring obesity.