In the context of child welfare, family reunification refers to the services that are provided for purposes of returning children who have been placed in out-of-home care to their families of origin. Family reunification is the primary permanency goal for the majority of children who have been placed temporarily outside of their homes. This literature review focuses on the federal Child and Family Services Review composite outcome indicator that seeks to measure agency performance related to family reunification. It describes factors at the level of the agency/system, the family, and the child that are associated with failure to reunify. Practices that have been linked with successful family reunification are described, with particular attention to the period between removal from the home and reunification. The review concludes with questions intended to promote discussion about the use of evidence to support the reunification process within child welfare agencies.