Incarcerated individuals are more likely to suffer from mental health and substance use disorders than the general population. Reentry is a particularly difficult time for individuals with SUDs as relapse may occur and is more likely to lead to overdose or death. This technical assistance package discusses the benefits of peer support in the criminal justice system and correctional facilities. Specifically, this document describes emerging and best practices for integrating peer support into correctional settings and provides recommendations for program design and implementation.