Preadolescents with a history of foster care placement report suicidal ideation at higher rates than their peers, which increases their risk for suicide attempts in adolescence. Despite these increased risks, few interventions have been shown to reduce suicidal ideation in these youth. This study examined the main and mediated long-term effects of a program to increase school readiness in children in foster care at age 5 years on suicidal ideation when the children were ages 9–11 years, 4 to 6 years after the intervention ended. Children who received the intervention were less likely to report suicidal ideation, although the difference did not reach statistical significance. The intervention reduced suicidal ideation indirectly through its positive effect on children’s self-esteem at age 9 years. Implications for programming to reduce suicidal ideation and subsequent suicide attempts in youth with a history of foster care are discussed.