Graduate students and postdoctoral researchers are increasingly taking on mentoring roles in undergraduate research (UR). There is, however, a paucity of research focusing on how they conceptualize their mentoring role. In this qualitative interview study, we identified three entry points that mentors reflect on to define their role: (1) What are the goals of UR? (2) What do the students expect from me? and (3) How should I use my expert knowledge? We discuss how academic developers can use these entry points together with a set of reflective lenses to stimulate critical reflection on the mentoring role and help the mentors to define their role and help the mentors to define their role.