Children exposed to intimate partner violence (IPV) are at high risk for adjustment problems, especially internalizing disorders. Few evidence-based interventions are available to address internalizing behavior problems in this population. An efficacy trial compared outcomes for 4–6 year old children randomly assigned to a program designed to address the effects of exposure to IPV with those allocated to a waitlist comparison condition. Mothers (N = 120) and children from the United States and Canada were assessed at baseline, 5 weeks later (post-intervention) and at 8-month follow-up. The evaluation compared rates of change over time for child internalizing problems. Results were analyzed using both intent-to-treat (ITT) and per-protocol (PP) approaches. ITT analyses indicated the program reduced internalizing problems for girls at follow-up. PP analyses indicated the program reduced internalizing problems for both boys and girls at post-intervention. In this study, child internalizing problems were significantly reduced through an intervention for the mother and the child.