IntroductionInadequate pain management in EDs is a worldwide problem, yet there has been little progress in understanding how pain management can be improved. There is only weak evidence and limited rationale to support interventions to improve pain management. We used naturalistic, qualitative methods to understand the factors that influence how pain is managed within the adult ED.MethodsWe used a multiple case study design incorporating 143-hour non-participant observation, documentary analysis and semistructured interviews with 37 staff and 19 patients at three EDs in the North of England between 2014 and 2016. We analysed data using thematic analysis.ResultsOur analysis demonstrated that pain management was not well aligned with the core priorities of the ED and was overlooked when other works took priority. We identified that (1) pain management was not perceived to be a key organisational priority for which staff were held accountable and staff had limited awareness of their performance, (2) pain management was not a core component of ED education and training, (3) ED processes and structures were not aligned with pain management and pain reassessment was overlooked unless staff escalated pain management outside of normal processes and (4) staff held embedded beliefs that conceptualised pain management as distinct from core priorities and limited their capacity to improve. However, EDs were able to improve pain management by aligning processes of pain management with other core works, particularly patient flow (eg, nurse-initiated analgesia at triage).ImplicationsEDs may be able to improve pain management by ensuring pain management processes align with key ED priorities. Undertaking multifaceted changes to structures and processes may enable staff to improve pain management and develop a culture in which pain management can be prioritised more easily. Future interventions need to be compatible with the wider work of the ED and enable patient flow in order to be adopted and maintained.