Background: Children and adolescents with disabilities often report low levels of physical activity (PA). Estimating the magnitude of PA disparities has been previously challenged by underreporting and variability in subsampling of disability. Using the National Survey of Children’s Health, this study estimated the population-level PA disparities experienced and the association between disability status and PA engagement. Methods: Weighted prevalence of PA engagement (National Physical Activity Guidelines for Americans (2nd edition) and sports participation) was compared across disability groups for children (n = 20,867, 6–11 y) and adolescents (n = 28,651, 12–17 y) and found to be 12%. Age-stratified multivariable logistic regressions estimated the likelihood of PA engagement as a function of disability status and type, after adjusting for child and household factors. Results: Children, but not adolescents, with disabilities had significantly lower odds of being sufficiently active compared with peers without disabilities (adjusted odds ratio = 0.75; 95% confidence interval, 0.60–0.94). Across age groups, the lowest prevalence rates were observed among those experiencing function and mobility disabilities. Children and adolescents were significantly less likely to participate in sports compared with peers. Conclusion: Children with function and mobility disabilities were identified as priority subpopulations least likely to be sufficiently active. The disparity in sports participation highlights a critical intervention point for increasing PA among children with disabilities.