This study examined whether Project Support, a parenting intervention shown to reduce child conduct problems, also exerts positive effects on features of psychopathy in children. Participants were 66 families (mothers and children) recruited from domestic violence shelters who participated in a randomized controlled trial evaluating Project Support. Each family included at least one child between the ages of 4 and 9 who was exhibiting clinical levels of conduct problems. Families were randomly assigned to the Project Support intervention condition or to an existing services comparison condition, and they were assessed on 6 occasions over 20 months, following their departure from the shelter. Children in families in the Project Support condition, compared with those in the comparison condition, exhibited greater reductions in features of psychopathy. Moreover, the changes in features of psychopathy remained after accounting for changes in conduct problems. Project Support’s effects on features of psychopathy were mediated by improvements in mothers’ harsh and inconsistent parenting. These findings on the effects of an intervention on features of psychopathy are the first from a randomized controlled trial. They inform the debate about whether features of psychopathy in children are responsive to intervention, and hold important implications for clinical practice.