Objectives Emergency medicine is a fast-growing medical profession. Nevertheless, the clinical activities emergency physicians (EPs) carry out and the responsibilities they have differ considerably between hospitals. This article addresses the question how the role of EPs is shaped and institutionalized in the everyday context of acute care in hospitals. Methods A cross-case ethnographic study was conducted, comprising observations, document analysis, and in-depth interviews in three emergency departments in the Netherlands. Results Drawing on the theoretical concept of institutional work, we show that managers, already established medical specialties, and EPs all conduct institutional work to enhance private interests, which both restricts and enlarges EPs’ work domain. These actions are strategic and intentional, as well as unintentional and part of EPs’ everyday work in acute care delivery. It is in this very process that tasks and responsibilities are redistributed and the role of the EP is shaped. Discussion In contemporary literature it is often argued that the role and status of EPs should be enhanced by strengthening regulation and improving training programs. This article shows that attention should also be paid to the more subtle everyday processes of role development.