The current study examines the social and behavioral development of school-age children with different histories of overweight onset. Eight thousand children from the Early Childhood Longitudinal Study-Kindergarten Cohort (ECLS-K) participated. Three groups of children were identified for analysis: (1) those who were persistently overweight from kindergarten and/or first grade through third grade; (2) those who were overweight only at third grade; and, (3) those who were never overweight between kindergarten and third grade. Models controlled for child, parent, and family characteristics and tested the linear and quadratic effects of time, the main effects of overweight group and gender, and the interactions among time, overweight group, and gender. Results revealed an effect of overweight on children's social and behavioral functioning, with several effects moderated by gender and time. Findings are discussed within the context of gender and development during early middle childhood. (Contains 3 footnotes, 4 tables and 4 figures.)