The current study examines the effects of Head Start on the development of school readiness outcomes for children living in non-parental care. Data were obtained from the Head Start Impact Study, a randomized controlled trial of Head Start conducted with a nationally representative sample of Head Start programs and families. The sample included 253 children living in non-parental care (defined as a primary caregiver who self-identified as someone other than a biological, adoptive, or step-parent), who experienced elevated rates of child and family risk factors. Results revealed modest direct short-term and indirect longer-term impacts of Head Start on school readiness outcomes (increased pre-academic skills, more positive teacher-child relationships, and reductions in behavior problems) for children living in non-parental care. Limitations of this study and directions for future research are discussed. (author abstract)