INTRODUCTION: Opioid use and dependence are prevalent among incarcerated people, contributing to elevated rates of overdose and other harms in this population. Opioid agonist treatment (OAT) has been shown to be an effective intervention to mitigate these risks. However, challenges to health care implementation in the custodial sector result in suboptimal and variable access to OAT in prisons nationally. MAIN RECOMMENDATIONS: Among a national multidisciplinary expert panel, we conducted a modified Delphi study that yielded 19 recommendations to government, relevant health authorities and custodial health services. These recommendations cover five core domains: induction or continuation of OAT, OAT options and administration, transition of care to the community, special populations, and organisational support. Key recommendations include prompt recognition and treatment of opioid withdrawal, active linkage to community-based OAT providers upon release, and ensuring appropriate organisational support through local protocols, adequate funding, and monitoring of key program indicators. CHANGES IN MANAGEMENT AS A RESULT OF THIS STATEMENT: This consensus statement addresses a significant gap in national policy on OAT in Australian prisons. The recommendations, finalised in July 2024, set forth best practice standards grounded in evidence and expert consensus. We expect that implementing these recommendations will enhance the quality, consistency and continuity of OAT both within prison and upon release. Optimising OAT provision is crucial for improving health outcomes and addressing the risk of overdose, which is the leading cause of death among people released from prison.