Policy debates about undocumented immigration in the United States focus most often on adults and adolescents. Yet 5.5 million U.S. children currently reside with at least one undocumented immigrant parent, with 4.5 million of these children U.S.-born citizens. Given that children with undocumented parents constitute nearly one-third of all children with immigrant parents and about 8 percent of all U.S. children, their well-being holds important implications for U.S. society. This review summarizes the current evidence on whether and how parent undocumented status affects the cognitive, school attainment, and mental health outcomes of children and youth. Research on mechanisms through which these effects occur--including both removal and fear of removal; parent-child separation; lower access to public programs; psychological distress; "awakening" to one's own undocumented status; and work conditions and economic hardship--is also reviewed. Potential moderators include the chronicity of experienced undocumented status; large-scale economic changes such as the Great Recession; and neighborhood and network social capital. Both public policies and community-based organizations' practices may help reduce the developmental risks for children with undocumented parents. We conclude by discussing a range of such policies and practices, related to preschool and prekindergarten, work and employment, border enforcement, program enrollment and access, organizational and institutional partnerships, and a range of choices regarding a pathway to citizenship. [This issue of "Social Policy Report" also includes the following commentaries: (1) All Our Children? (Ruby Takanishi); (2) The Plight of the Children of Unauthorized Mexican Parents (Frank D. Bean); and (3) Children in the U.S. with Undocumented Parents: Research and Policy Issues (Alexander N. Ortega).]