Positive teacher-child relationships, characterized by warmth and closeness, are associated with better behavioral and academic outcomes for children in preschool and elementary school (Hamre & Pianta, 2005). Supporting teachers to establish these positive relationships with children is important in all early care and education (ECE) programs. Head Start programs, designed to address the needs of the whole child, including healthy relationships with teachers, may be particularly effective in facilitating positive teacher-child relationships (Zigler & Styfco, 2010). The current study examined the role of Head Start in supporting teachers in establishing more positive and less conflictual relationships with children, including potential mechanisms of influence, and moderation by children's levels of problem behaviors. The study utilized data from the Head Start Impact Study, a nationally representative randomized control trial of 4,442 Head Start-eligible children and families assigned to either Head Start (n= 2,783) or a community control group (n= 1,884; U.S. DHHS, 2010a). No significant direct effect of Head Start on teacher-child closeness was detected. Indirect effects of Head Start on teacher-child relationships mediated through teacher supports and mentoring were only found for children without problem behaviors. Findings from the current study suggest a greater need for professional development efforts, specifically providing strategies effective in managing children with problem behaviors. (author abstract)