There is a national opioid epidemic and one intervention to help those suffering from an opioid use disorder (OUD) is medication-assisted treatment (MAT). MAT is the use of medications in conjunction with behavioral therapy as part of a long-term treatment regimen. There are three main MAT medications used today—methadone, buprenorphine, and naltrexone. Research has shown MAT, in particular the use of methadone or buprenorphine, is considered an evidence-based practice to treat OUD. Studies indicate those in MAT have better outcomes than those who engage in therapy alone. This article provides an overview of MAT with a focus on use with criminal justice populations.