To evaluate outcomes after major surgery in children and adolescents with intellectual disability. METHOD We used 2004 to 2013 claims data from Taiwan's National Health Insurance programme to conduct a nested cohort study, which included 220 292 surgical patients aged 6 to 17 years. A propensity score matching procedure was used to select 2173 children with intellectual disability and 21 730 children without intellectual disability for comparison. Logistic regression was used to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of the postoperative complications and 30-day mortality associated with intellectual disability. RESULTS Children with intellectual disability had a higher risk of postoperative pneumonia (OR 2.16, 95% CI 1.48-3.15; p<0.001), sepsis (OR 1.67, 95% CI 1.28-2.18; p<0.001), and 30-day mortality (OR 2.04, 95% CI 1.05-3.93; p=0.013) compared with children without intellectual disability. Children with intellectual disability also had longer lengths of hospital stay (p<0.001) and higher medical expenditure (p<0.001) when compared with children with no intellectual disability.