Although children with incarcerated parents exhibit more behavior problems, health concerns, and academic difficulties than their peers, few interventions or resources are available to support affected children. This randomized, controlled, multisite efficacy trial evaluated Sesame Street’s "Little Children, Big Challenges: Incarceration" initiative with children aged 3 to 8 years with a jailed father. Seventy-one diverse children and their caregivers were randomized to an educational outreach group ( n = 32) or wait list control group ( n = 39). Researchers observed children during jail visits and interviewed caregivers by phone 2 and 4 weeks later. The effects of the intervention on children’s behavior and emotions occurring during a jail visit depended on what children had been told about the father’s incarceration. Children who were told honest, developmentally appropriate explanations showed less negative affect at entry, an increase in negative affect when the intervention was administered, and a decrease in negative affect during the visit. Intervention group children who were told distortions, nothing, or explanations that were not developmentally appropriate showed more negative affect initially, and their negative affect remained relatively stable during their time in the jail. In addition, children who were told the simple, honest truth about the parent’s incarceration (a recommendation in the educational materials) exhibited more positive affect during the visit, with a medium effect size. Caregivers in the educational outreach group reported more positive change in how they talked to children about the incarceration over time compared to the control group.