In this population-based study, prevalence of depression was estimated and compared between children with and without developmental disability (DD). Twelve years of administrative data were linked to identify a cohort of children with DD living in the Canadian province of Manitoba. Children in the study cohort were matched with children without DD as to sex, age, and region of residence. Prevalence of depression was estimated and compared between the two groups using the Generalized Estimating Equations technique. It was found that the estimated prevalence of depression among children with DD was almost twice as high as that of children in the matched comparison group. The estimated relative risk was statistically significant, RR = 2.13 (95% CI: 1.94, 2.33, p < 0.001). With age, the prevalence of depression among children in both groups increased. These findings suggest an urgent need for the development of mental health promotion programs targeted at children with DD.