We report a graded relationship between neighborhood socioeconomic status (SES) and children's antisocial behavior that (a) can be observed at school entry, (b) widens across childhood, (c) remains after controlling for family-level SES and risk, and (d) is completely mediated by maternal warmth and parental monitoring (defined throughout as supportive parenting). The children were participants in the Environmental Risk Longitudinal Twin Study (N = 2,232), which prospectively tracked the development of children and their neighborhoods across childhood. Direct and independent effects of neighborhood-level SES on children's antisocial behavior were observed as early as age 5, and the gap between children living in deprived versus more affluent neighborhoods widened as children approached adolescence. By age 12, the effect of neighborhood SES on children's antisocial behavior was as large as the effect observed for our most robust predictor of antisocial behavior: sex (Cohen d = 0.51 when comparing children growing up in deprived vs. more affluent neighborhoods in comparison to Cohen d = 0.53 when comparing antisocial behavior among boys vs. girls). However, these relatively large differences in children's levels and rate of change in antisocial behavior across deprived versus more affluent neighborhoods were completely mediated by supportive parenting practices. The implications of our findings for studying and reducing socioeconomic disparities in antisocial behavior among children are discussed.