Purpose: This paper presents an analysis of Head Start (HStart) preschooler data by severity of developmental concern, while considering socio-demographic and other factors that highlight racial and ethnic disparities in the early identification of developmental delay or disability (DD). Design and methods: We conducted an analysis of 2014–2015 academic year data for preschool-aged children in HStart in both urban and suburban centers in a large Midwestern city. Descriptive statistics were used to determine the prevalence of developmental concerns and compare characteristics of children with mild-to-moderate versus severe developmental concerns; differences between groups were compared using t-tests and chi-square tests. Multivariate logistic regression was used to determine the independent effect of each predictor of concern severity. Results: Nearly one-third of HStart preschoolers were identified with developmental concern; 70% were mild-to-moderate risk for DD and the remaining severe risk. Neither group was routinely referred to healthcare for evaluation or treatment, and most of the severe risk group did not qualify nor receive treatment for DD with an Individualized Education Plan. Suburban and urban preschoolers with severe concern were less likely to be African American or Latinx, suggesting that racially and ethnically diverse preschoolers in HStart may be under-identified and under-treated. Conclusions: Lags in the educational diagnosis of DD may mirror the disparities in diagnosis and treatment of DD among minority groups. Primary care is the first line for detection and treatment of DD, and offers a unique opportunity to act for racially and ethnically diverse HStart preschoolers disproportionately at-risk for DD. (author abstract)