IMPORTANCE Traumatic brain injury (TBI) in children results in a high number of emergency department visits and risk for long-term adverse effects. OBJECTIVES To estimate lifetime prevalence of TBI in a nationally representative sample of US children and describe the association between TBI and other childhood health conditions. DESIGN, SETTING, AND PARTICIPANTS Data were analyzed from the 2011-2012 National Survey of Children's Health, a cross-sectional telephone survey of US households with a response rate of 23%. Traumatic brain injury prevalence estimates were stratified by sociodemographic characteristics. The likelihood of reporting specific health conditions was compared between children with and without TBI. Age-adjusted prevalence estimates were computed for each state. Associations between TBI prevalence, insurance type, and parent rating of insurance adequacy were examined. Data analysis was conducted from February 1, 2016, through November 1, 2017. MAIN OUTCOMES AND MEASURES Lifetime estimate of TBI in children, associated childhood health conditions, and parent report of health insurance type and adequacy. RESULTS The lifetime estimate of parent-reported TBI among children was 2.5% (95% CI, 2.3%-2.7%), representing over 1.8 million children nationally. Children with a lifetime history of TBI were more likely to have a variety of health conditions compared with those without a TBI history. Those with the highest prevalence included learning disorders (21.4%; 95% CI, 18.1%-25.2%); attention-deficit/hyperactivity disorder (20.5%; 95% CI, 17.4%-24.0%); speech/language problems (18.6%; 95% CI, 15.8%-21.7%); developmental delay (15.3%; 95% CI, 12.9%-18.1%); bone, joint, or muscle problems (14.2%; 95% CI, 11.6%-17.2%); and anxiety problems (13.2%; 95% CI, 11.0%-16.0%). States with a higher prevalence of childhood TBI were more likely to have a higher proportion of children with private health insurance and higher parent report of adequate insurance. Examples of states with higher prevalence of TBI and higher proportion of private insurance included Maine,