Background: Childhood overweight is a condition that is prevalent within our society, affecting more and more children each year. The purpose of this study was to examine the relationship between child overweight and educational outcomes. Methods: Data are reported for 13,680 children in third grade from the Early Childhood Longitudinal Study, a set of data designed and carried out by the US Department of Education. Students were individually administered reading and math assessments. Teachers reported how often students exhibited certain social skills and behaviors. A series of 1-way analyses of covariance and multivariate analysis of covariance was used. Results: Overweight children had significantly lower math and reading test scores compared with nonoverweight children in third grade. However, these differences became insignificant after including socioeconomic and maternal education variables. Third grade overweight girls had significantly more externalizing and internalizing problems as well as lower self-control scores than nonoverweight girls even after including socioeconomic and maternal education variables. Conclusions: Findings suggest that how we deal with children's overweight may have implications for the future psychological health of a considerable proportion of US children. (Contains 2 tables.)