This study examined children’s exposure to family adversity, hostile reactivity to parental conflict, and negative family representations as mediators of the prospective relation between their temperamental exuberance and externalizing symptoms. Participants included 243 preschool children (Mage = 4.60 years; 56% girls) and parents (48% Black; 16% Latinx) in a multi-method and multi-informant study with three annual measurement occasions. Structural equation model results specifically supported children’s hostile reactivity to parental conflict and negative family representations as mediators. Exuberance predicted residualized increases in children’s hostile reactivity and negative family representations over a 1-year period. In turn, children’s hostile reactivity and negative family representations predicted their greater externalizing symptoms 1 year later after controlling for prior externalizing symptoms. Results are discussed in the context of their relation and refinement of temperamental models of developmental psychopathology.