Child social-emotional development is foundational for future success, and depends on the presence of caregiver–child relationships characterized by positive “serve and return” interactions, during which caregiver responses are reliable, consistent, and empathic. Caregivers with childhood trauma may be limited in their ability to provide this type of interaction, and child social-emotional development may be at risk. We describe a Healthy Steps (HS) program and the moderating effect of this program on the relationship between reported caregiver childhood trauma and child social-emotional development. In a quasi-experimental, longitudinal design, we determined the relationship between maternal report of childhood trauma and child social-emotional development on the Ages and Stages Questionnaires: Social-Emotional (ASQ:SE) at 36 months, adjusting for covariates, and tested for a moderating effect of participation in HS on this relationship. One hundred twenty-four children were assessed at 36 months. Children of mothers with childhood trauma had higher (worse) ASQ:SE mean scores than children of mothers without childhood trauma (75.9 vs. 35.9; p < .0001). Differences in adjusted mean ASQ:SE scores between children of mothers with and without childhood trauma were more apparent in the comparison group (90.4 vs. 28.3) than in HS (44.5 vs. 28.2; p < .001). Caregiver experiences of childhood trauma are related to deficits in social-emotional development in their 3-year-old children. HS, with a focus on caregiver trauma and child social-emotional development, may serve as a moderator of this association.