Key PointsQuestionWhat factors are associated with racial and ethnic differences in the risk of developing tooth decay among US children?FindingsThis cohort study of 61 083 children and adolescents found that compared with White children, all other racial and ethnic groups among those aged 0 to 5 years, Hispanic and Black children among those aged 6 to 10 years, and Black adolescents among those aged 11 to 18 years were at a higher risk of tooth decay. Mediation analysis revealed that individual- and community-level factors, including insurance and dental procedure types, explained most racial and ethnic disparities in the risk of tooth decay.MeaningThese findings suggest that efforts to reduce racial and ethnic disparities in tooth decay should target different individual- and community-level factors, depending on age and racial and ethnic group.