Background: Previous research on psychiatric and health disparities according to level of cognitive functioning has focused on adults within an American healthcare context. The current study compares children with and without cognitive and developmental delays in Quebec, Canada, using physician billing data from a longitudinal study of low-income, francophone families. Canada is an ideal context for studying medical billing data as its equal access healthcare system removes many socioeconomic biases. Methods: A large sample (n = 1050) of children is used to describe psychiatric and health disparities, as well as differences in Ambulatory Care Sensitive (ACS) conditions and primary healthcare, between children with (n = 107) and without (n = 943) diagnoses in their billing history indicative of delays. Results: The findings demonstrated a relatively high level of psychiatric diagnoses for children with delays. However, no difference was found between children with and without delays in regard to emergency room visits and hospitalizations for ACS conditions and primary healthcare. Conclusions: The findings suggest that, within a universal healthcare system, disparities in primary healthcare may not emerge until adulthood in individuals with delay status.