Children who have experienced early adversities are at risk for behavioral problems and trauma symptoms. Using a two-group, pre-post intervention design, the current study evaluated the effectiveness of a parent training utilizing Trust-Based Relational Intervention, a trauma-informed, attachment-based intervention, in reducing behavioral problems and trauma symptoms in at-risk adopted children. Children of parents in the treatment group (n = 48) demonstrated significant decreases in behavioral problems on the Strengths and Difficulties Questionnaire and significant decreases in trauma symptoms on the Trauma Symptoms Checklist for Young Children after intervention. Scores for children in a matched-sample control group did not change. Findings suggest that Trust-Based Relational Intervention is effective at addressing many behavioral problems and trauma symptoms in children with histories of adversities.