Research conducted over the past two decades has shown that young people transitioning to adulthood from custodial care systems, such as the child welfare and juvenile justice systems, are at particularly high risk of experiencing poor outcomes. Despite considerable government investment in supporting the transition to adulthood for these youth, the evidence base to inform those investments remains limited. The study reported here uses a random-assignment evaluation design to assess the impact of the YVLifeSet program on young adults transitioning to adulthood from the child welfare and juvenile justice systems in the state of Tennessee. The evaluation identified positive impacts of the program on employment and earnings, housing instability, economic hardship, and health and safety. However, the program had no impact on measures of education, social support, criminal behavior and justice system involvement. The study findings provide guidance for future research and program development and raise questions about the appropriateness of traditional models of case management for transition-age youth.