This paper presents the findings of a randomized control trial involving children under 3 years of age and their mothers who were identified as being at risk of maltreating their children by referral agencies. Mothers’ risk status derived from a heavy trauma burden, mental health challenges, and/or prior removal of a child to foster care. Mothers were randomly assigned to either a widely used parenting class known as Systematic Training for Effective Parenting (STEP) or the Group Attachment-Based Intervention (GABI), a multifamily 26-week treatment. In comparison to STEP, results indicated that GABI was linked to significant improvements in maternal supportive presence and dyadic reciprocity, as well as significant declines in maternal hostility and dyadic constriction (proxies for risk of child maltreatment). The study also showed the importance of using treatments that are sensitive to parents’ traumatic histories.