This study examined children's attention biases to negative emotional stimuli as mediators of associations between interparental hostility and children's externalizing symptoms. Participants included 243 children (M[subscript age] = 4.60 years) and their parents and teachers across three annual measurement occasions. Cross-lagged latent change analyses revealed that the association between interparental hostility and children's externalizing symptoms was mediated by children's attention to angry, but not sad or fearful, adult faces. Consistent with defensive exclusion models, the multimethod, multi-informant assessment of interparental hostility at Wave 1 specifically predicted decreases in children's attention to angry faces from Waves 1 to 2 in a visual search task. Declines in children's attention to anger, in turn, predicted increases in teacher reports of their externalizing problems across the three waves. Follow-up analyses further indicated that children's decreasing levels of emotional security in the interparental relationship were associated with the decreases in children's attention to angry stimuli. Results are discussed in relation to how they inform and advance information processing and social threat models in developmental psychopathology.