Research Findings: Exuberant temperament, characterized by high approach and positive affect, is linked to socioemotional outcomes including risk of externalizing symptoms across development. Externalizing problems interfere with children's school readiness and lead to disruptive behavior in the classroom. While some moderating factors help identify which exuberant children are at risk and in which contexts they are at risk, few studies have identified early moderators that protect against maladjustment when children enter school. In the current study, we examined exuberant temperament in 124 toddlers and classroom behavior problems reported by kindergarten teachers. We also assessed the impact of maternal responsiveness at 24 months on the relation between exuberance and classroom behavior problems. As hypothesized, we found that higher exuberance predicted more behavior problems. In addition, maternal responsiveness moderated this association such that high responsiveness protected exuberant children from classroom behavior problems. Practice or Policy: These results expand our understanding of socioemotional risks for exuberant children and how these risks influence school readiness. We also find that maternal responsiveness during toddlerhood mitigates these risks, and our findings suggest that interventions for exuberant children at risk for behavior problems or poor school readiness should target parental responsiveness when children are toddlers.