Weak coordination between community correctional agencies and community-based treatment providers is a major barrier to diffusion of medication-assisted treatment (MAT)--the inclusion of medications (e.g., methadone and buprenorphine) in combination with traditional counseling and behavioral therapies to treat substance use disorders. In a multisite cluster randomized trial, experimental sites (j = 10) received a 3-h MAT training plus a 12-month linkage intervention; control sites (j = 10) received the 3-h training alone. Hierarchical linear models showed that the intervention resulted in significant improvements in perceptions of interagency coordination among treatment providers, but not probation/parole agents. Implications for policy and practice are discussed.