The additive and synergistic effects of a parent-peer model in the development of child antisocial behavior from the ages of 5 to 7 was examined. Participants included a community sample of 267 children at kindergarten entry, 134 boys and 133 girls. Participants’ mean age was 5.3 years at the start of data collection (fall of kindergarten), with final data collection in the spring of first grade (mean age 7.2 years). Multi-method, multi-informant methods were used to examine skilled and unskilled parenting, as well as peer processes, including coercion, rejection, and deviancy training to the development of overt and covert antisocial behavior. Both ineffective parenting and deviant peer processes were related to chronic levels of covert and overt antisocial behavior, but peer processes contributed in a stronger fashion. However, only ineffective parenting processes reliably predicted individual differences in children’s growth in overt and covert antisocial behavior. These results support the notion that interventions may need to target social processes in multiple settings, to include parents and peers, and perhaps teachers. Further implications for prevention and intervention are discussed.