This article addresses methodological approaches to the study of vulnerable cohorts with specific attention to definitions of the term vulnerability. In particular, it investigates the issue of adults, particularly women, who have experienced abuse in the Catholic Church. Relevant analysis in this area is primarily interdisciplinary-based research and includes sociological and psychological perspectives and theological and historical analysis. This article critically analyzes the current definitions of vulnerability in Church and research contexts, and the methodological approaches utilized in defining vulnerable cohorts. It argues that specific ethical principles and methodological strategies are required to safeguard participants and researchers guided by the principles of feminist ethics. These include (1) attention to the uses and definitions of key terms by participants and researchers; (2) identifying the positionality of researchers as central to an ethical standpoint including their exposure to secondary trauma; and (3) establishing inclusive methods such as participatory research and sensitive recruitment. Paying attention to ongoing issues experienced by cohorts identified as vulnerable in research, including the stigmatization of their status, marginalization of their cases, and trauma of disclosure alongside ongoing risk assessment, is central to the research design process.