A behaviorally-uninhibited temperament, callous-unemotional (CU) features, and harsh parenting have been associated with specific patterns of aggressive behavior in older children and adolescents. We tested the additive and interactive effects of these factors in predicting different types of aggressive behavior in a high-risk preschool sample. Forty-nine preschoolers and their parents registering for Head Start programs were recruited for participation. Behavioral inhibition, CU features, and attitudes toward various types of parenting were assessed through parent rating scales completed at the time of registration. Behavioral inhibition, CU features, and aggression were assessed by teacher ratings approximately six months later. Analyses revealed that behavioral inhibition, CU features, and harsh parental attitudes all contributed independently to the prediction of aggressive behavior. These associations were strongest for proactive types of aggression. Our results suggest that a behaviorally uninhibited temperament, CU features, and attitudes favoring harsh parenting are all important for understanding the development of aggression in preschool children.