Diabetic ketoacidosis is the leading cause of death among children with type 1 diabetes mellitus, and is an avoidable complication at first-time diagnosis of diabetes. Because having a usual provider of primary care is important in improving health outcomes for children, we tested the association between having a usual provider of care and risk of diabetic ketoacidosis at onset of diabetes. Using linked health administrative data for the province of Quebec, we conducted a population-based retrospective cohort study of children aged 1-17 years in whom diabetes was diagnosed from 2006 to 2015. We estimated adjusted risk ratios (RRs) for an episode of diabetic ketoacidosis at the time of diabetes diagnosis in relation to usual provider of care (family physician, pediatrician or none) using Poisson regression models with robust error variance. We identified 3704 new cases of diabetes in Quebec children from 2006 to 2015. Of these, 996 (26.9%) presented with diabetic ketoacidosis. A decreased risk of this complication was associated with having a usual provider of care; the association was stronger with increasing age, reaching statistical significance among those aged 12-17 years. Within this age group, those who had a family physician or a pediatrician were 31% less likely (adjusted RR 0.69, 95% confidence interval [CI] 0.56-0.85) or 38% less likely (adjusted RR 0.62, 95% CI 0.45-0.86), respectively, to present with diabetic ketoacidosis, relative to those without a usual provider of care. For children with newly diagnosed diabetes, having a usual provider of care appears to be important in decreasing the risk of diabetic ketoacidosis at the time of diabetes diagnosis. Our results provide further evidence concerning the need for initiatives that promote access to primary care for children.