Child obesity poses short- and long-term health risks and may have negative social and economic consequences in adulthood. This study uses data on 8,000 children followed from kindergarten through third grade as part of the Early Childhood Longitudinal Study-Kindergarten Class to examine predictors of persistent childhood overweight and associated academic and socioemotional outcomes. Results show that socioeconomic status, gender, race, and behavioral and environmental factors influence risk of persistent overweight. The odds of children being overweight increased 3 percent for each additional hour of television that they watched per week and 9 percent for each family meal per week that they did not experience. Overweight children progressed less than their nonoverweight peers did in reading and math achievement, with overweight appearing to precede academic difficulties, and were rated lower on academic and socioemotional factors by their teachers and themselves. Academic and social costs should be considered in assessing costs of childhood overweight and potential benefits of overweight prevention.