OBJECTIVE : This study examined the long-term effects of Head Start on foster children's developmental outcomes from ages 3-4 to 8-9. METHODS : 187 children in the care of foster parents (either relatives or non-relatives) were selected among 4442 children from the Head Start Impact study data, collected during 2002-2009. Children's cognitive, social-emotional, and health outcomes were measured at three time points: ages 3-4, 5-6, and 8-9. RESULTS : Regression analysis was used to examine interaction effects of Head Start at the three measured time points. Results indicated that children in foster care who participated in Head Start had overall higher cognitive, social-emotional, and health outcomes compared to children in foster care who did not participate in Head Start. The positive impacts of Head Start on children in foster care were more prevalent when children were 8-9 years old. CONCLUSIONS : Social workers should evaluate, identify and connect adequate social services to children in foster care. Future studies should be conducted to identify the barriers of accessing Head Start among children in foster care.