This exploratory study of 23 parent–child dyads receiving child welfare services examined the association between the number of adverse childhood experiences (ACEs) parents reported and their children’s externalizing behaviors. We also assessed whether the effects of Parent-Child Interaction Therapy (PCIT) on externalizing behaviors varied by parents’ ACE histories. Results indicated that parents’ ACE scores were associated with child externalizing symptoms at baseline, but not at a second postbaseline assessment. Although all parents reported reductions in child externalizing behavior from baseline to postbaseline, only reductions reported by parents with four or more ACEs were statistically significant. Implications for implementing PCIT with trauma-exposed families are discussed.