The current study examined whether parent psychological resources (parenting stress, depression, and social support from friends and family) moderated the effects of early family preventive intervention on parenting among high-risk families. Ninety-two preschool-age children (M age = 3.94 years) at familial risk for conduct problems participated in a randomized controlled trial of a family intervention to prevent conduct problems. The majority of families were African American or Latino and experienced multiple stressors associated with poverty and familial antisocial behavior. Families were randomized to a 22-session group-based intervention or to a no-intervention, assessment-only control condition. Parents reported on their psychological resources (parenting stress, depression and social support from friends and family) at baseline. Parenting (responsive, harsh, stimulation for learning) was assessed through self-report and observational measures four times over 24 months. Previously-reported intervention effects on responsive parenting and stimulation for learning were moderated by depression and social support from friends, respectively, such that benefits were concentrated among those at greatest risk (i.e., depressed, limited support from friends). The intervention effect on harsh parenting was not moderated by any of the parent psychological resources examined, such that parents with high and low resources benefited comparably. Consideration of moderators of preventive intervention effects on parenting provides important information about intervention impact among families experiencing multiple barriers to engagement and effective parenting. Findings suggest that parents with diminished psychological resources are just as likely to benefit. Family-focused, group-based intervention is promising for strengthening parenting among the highest risk families.