Variations in parents' emotion socialization have been linked to children's social competence (SC) and behavior problems, but parental influences do not act independently of children's characteristics. A biopsychosocial model was tested, in which children's parasympathetic regulation of cardiac function and paternal and maternal socialization of negative emotions were examined as joint predictors of young children's SC and behavior problems at daycare and preschool. Mothers and fathers responded differently to children's emotions, and cardiac vagal tone moderated the relations between parents' emotion socialization and children's behavior in early childcare settings. Both maternal and paternal emotion socialization strategies were more strongly associated with preschool adjustment for children with relatively less parasympathetic self-regulatory capacities than for more self-regulated children. Paternal reactions to children's anger, and maternal responses to children's sadness and fear, were particularly closely tied to variations in SC and internalizing and externalizing problems.