Despite knowledge of early pathways to conduct problems, few preventive interventions are specifically designed to modify disruptive behavior in toddlerhood. One potential prevention target is proactive and positive parenting, which is associated with reduced risk of conduct problems in preschoolers. This randomized trial with 120 low-income 2-year-old boys examined whether a brief family-centered intervention that reduces disruptive behavior (D. Shaw, T. Dishion, L. Supplee, F. Gardner, & K. Arnds, 2006) also leads to increases in proactive and positive parenting. It also explored whether change in parenting predicts change in disruptive behavior. In the intervention group, proactive and positive parenting skills increased among parents of 3-year-olds. Change in proactive and positive parenting of 2- to 3-year-old toddlers correlated with change in child disruptive behavior, although the mediation effect of positive parenting was of only borderline significance. Findings suggest that even within a brief and multifaceted preventive intervention, change in proactive parenting skills contributes modestly but significantly to change in child problem behavior.