Moral distress denotes a negative reaction to a morally challenging situation. It has been associated with adverse outcomes for healthcare professionals, patients and healthcare institutions. We argue that existing definitions, along with measures of moral distress, compromise the validity of empirical research. First, the definition and measurement of moral distress conflate moral events and psychological distress, even though they are distinct phenomena that should be assessed independently. Second, in many studies, there is a lack of clarity in distinguishing between moral and non-moral events. Finally, prior research on moral distress often overlooks the substantial body of evidence demonstrating the impact of diverse work-related factors, beyond moral events, on both distress and job retention. These challenges might undermine the effectiveness of interventions aimed at alleviating moral distress. We outline a comprehensive research agenda that encompasses conceptual clarifications, the refinement of data collection instruments, the design of studies and the application of appropriate statistical methods.