Abstract: The concept of vulnerability plays a central role in research ethics in signaling that certain research participants warrant more careful consideration because their risk of harm is heightened due to their participation in research. Despite scholarly debates, the descriptive and normative meanings ascribed to the concept have remained disengaged from the perspective of users of the concept and those concerned by its use. In this study, we report a survey- and interview-based investigation of mental health researcher perspectives on vulnerability. We found that autonomy-based understandings of vulnerability were predominant but that other understandings coexisted, reflecting considerable pluralism. A wide range of challenges were associated with this concept, and further training was recommended by researchers.