Improving coordination among state agencies overseeing the juvenile justice, mental health, and Medicaid systems is crucial to improving access to quality health services for juvenile justice-involved youth. This paper describes the core concepts of the three state-administered programs with major responsibilities for serving these children juvenile justice, mental health, and Medicaid, and highlights both the barriers and opportunities for working across agencies to use Medicaid to meet these children’s health needs, as identified in interviews with stakeholders in the Models for Change states.