Introduction: The opioid crisis persists, and in the context of this urgency and new practice guidelines, the practice of buprenorphine (BUP) prescription is expanding across Canadian emergency departments (EDs). The objective of this study was to identify current knowledge, attitudes and behaviours to managing opioid use disorder (OUD) in the ED, including barriers and facilitators to prescribing BUP. Methods: Forty ED staff physicians were randomly invited to participate from an urban Toronto ED which recently received continuing medical education in addictions, and whose hospital established an addictions follow-up clinic. Individual semi-structured interviews with the 19 physicians who self-selected to participate were grounded in phenomenology, allowing for in-depth accounts of participants’ lived experience and viewpoints on their role in addressing OUD. Thematic analysis was achieved through multiple readings; themes were coded using Dedoose software by two researchers. Themes were further organized as facilitators, barriers, and proposed solutions. Results: Opioid withdrawal management in the ED varied significantly between these practitioners in the same practice group. Facilitators to treating withdrawal and initiating BUP in the ED were rooted in three contributors to physician empowerment: knowledge about OUD and BUP, positive patient and provider experience with substitution therapy in the past, and exposure to physician champions to guide their practice. Systems-level facilitators included timely access to follow-up care and an available order set. Barriers included provider inexperience: missing subtle presentations of withdrawal, lacking feedback on treatment effectiveness, and reported uncertainty about the protocol from nursing staff. The ED environment also limits time to counsel effectively and discourages taking up a bed both to wait for withdrawal onset and for BUP induction. Other barriers were concerns about precipitating withdrawal, prescribing a chronic medication in acute care, and patient attitudes. Conclusion: This is the first study describing barriers and facilitators to addressing OUD and prescribing BUP in the ED. These findings suggest a role for home induction, involvement of allied health professionals in BUP counseling, and heightened continuing medical education. Results will inform departmental efforts across Canada to implement BUP prescribing as standard of care for patients in opioid withdrawal.