Objective: To assess budget impact of the introduction of prolonged-release buprenorphine (PRB) for care of opioid use disorder (OUD) over 1 year in a defined population. Materials and Methods: A healthcare perspective, decision-tree model analysis of the cost of OUD care for a standard population was prepared to compare two scenarios: treatment of a population under the existing standard of care, or with the addition of PRB. The model assessed OUD-related direct costs (medication, delivery, psychosocial treatment), other services costs (harm reduction, general healthcare, social and justice services) and the impact of behaviors such as engaging with treatment and electing to use additional opioids "on top" of treatment regimens, and "dropping out" from treatment. Results: Standard population definition (persons offered OUD care services) is based on a typical administrative region in England with general population of 400,000 citizens, 1,777 high-risk opioid users requiring treatment and 909 patients initiating treatment in a year. The cost to provide OUD care for 1 year under the current scenario (70% treated with methadone, 30% sublingual buprenorphine) is £19.7M. In scenarios with increased PRB adoption/reduced sublingual buprenorphine or oral methadone use, the cost reduction ranges from £0.2M to 0.7M. Conclusion: The assessment showed a reduction of overall costs after introduction of PRB.