This randomized controlled trial tested an enhanced model of Early Head Start (EHS) that combined home-based EHS with Attachment and Biobehavioral Catch-up (ABC; Dozier & Bernard, 2017), a brief, attachment-based intervention. The trial included 208 low-income mothers (87% Latina) and their 6- to 18-month-old infants. Control participants received home-based EHS plus 10 weekly books. Follow-up observations revealed positive impacts of the enhanced EHS plus ABC model on maternal sensitivity/responsiveness, intrusiveness, and positive regard (ds = 0.23-0.77). Exploratory analyses of moderated effects suggested stronger impacts for those mothers who began the study with greater intrusiveness or who described their adult attachment style as secure or anxious. Findings are discussed in terms of implications for improving effects on parenting of publicly funded programs designed to support early development.