The US Department of Housing and Urban Development (HUD)‘s Family Unification Program (FUP) provides low-income families involved in the child welfare system with housing vouchers. FUP is an important vehicle for understanding three issues: (1) the overlap between the child welfare system, housing, and homelessness; (2) how to provide housing to vulnerable, high-need families; and (3) how to facilitate cross-system partnerships between public housing agencies and child welfare agencies. The Urban Institute studied FUP design and implementation in eight sites and interviewed key staff and stakeholders about the program’s implementation and impact, highlighting common challenges, innovative practices, and system-level impacts.