OBJECTIVES: To study the national prevalence of 10 developmental disabilities in US children aged 3 to 17 years and explore changes over time by associated demographic and socioeconomic characteristics, using the National Health Interview Survey. METHODS: Data come from the 2009 to 2017 National Health Interview Survey, a nationally representative survey of the civilian noninstitutionalized population. Parents reported physician or other health care professional diagnoses of attention-deficit/hyperactivity disorder; autism spectrum disorder; blindness; cerebral palsy; moderate to profound hearing loss; learning disability; intellectual disability; seizures; stuttering or stammering; and other developmental delays. Weighted percentages for each of the selected developmental disabilities and any developmental disability were calculated and stratified by demographic and socioeconomic characteristics. RESULTS: From 2009 to 2011 and 2015 to 2017, there were overall significant increases in the prevalence of any developmental disability (16.2%-17.8%, P , .001), attention-deficit/ hyperactivity disorder (8.5%-9.5%, P , .01), autism spectrum disorder (1.1%-2.5%, P , .001), and intellectual disability (0.9%-1.2%, P , .05), but a significant decrease for any other developmental delay (4.7%-4.1%, P , .05). The prevalence of any developmental disability increased among boys, older children, non-Hispanic white and Hispanic children, children with private insurance only, children with birth weight $2500 g, and children living in urban areas and with less-educated mothers. CONCLUSIONS: The prevalence of developmental disability among US children aged 3 to 17 years increased between 2009 and 2017. Changes by demographic and socioeconomic subgroups may be related to improvements in awareness and access to health care. WHAT'S KNOWN ON THIS SUBJECT: Previously, researchers found health disparities in diagnosed developmental disabilities by demographic and socioeconomic characteristics among US children. Changes in awareness, knowledge, health care services access, and improved measurement make it important to continue to monitor prevalence changes in the population. WHAT THIS STUDY ADDS: With this study, we present new nationally representative data on the prevalence of developmental disability, recent demographic trends, and estimates by urban or rural residence.