Little is known about how research assistants (RAs) protect participants in vulnerable circumstances. Using a critical qualitative method informed by feminist ethics, we ran five focus groups with experienced RAs. We identified two themes: (a) expressing moral competencies (subthemes: recognizing power, privilege, and vulnerability; adapting processes and providing support; understanding the sources of moral competencies) and (b) negotiating and making transparent roles and responsibilities (subthemes: separating responsibilities as a clinician from those of an RA; critically reflecting on the shared responsibilities of principal investigators and RAs; and identifying the role of the Research Ethics Committee). Although RAs possess a variety of moral competencies and have an important role in protecting research participants in vulnerable circumstances, that role is largely unrecognized.