To explore how mentors perceive and perform their role in a longitudinal mentorship programme with the objective of guiding medical students in becoming reflective learners. A qualitative exploratory study was conducted using semi-structured interviews with 16 mentors from the Ghent University medical education mentoring programme. Participants were selected by purposeful sampling on gender, years of experience and area of specialisation. Interview transcripts were analysed using inductive thematic analysis. Afterwards, all transcripts were re-analysed combining the resulting themes to identify different mentoring profiles. Our analysis yielded three themes. First, the basic conditions for mentorship showed wide differences in competencies that mentors considered necessary. Second, goals and purposes of mentoring identified roles ranging from ombudsperson, confidential advisor, role model to guide towards professional and personal growth. Third, attitudes to the mentoring programme revealed a wide variation from fully embracing to rejecting the reflective method. Further analysis led to three mentor profiles: reflective, sharing and advising. Even reflective mentors struggled in varying degrees with applying the guidelines, mostly depending on prior experience with reflection. Advising mentors found the intervision techniques too constrictive and expressed doubts about the usefulness of the programme. In this reflection-based mentoring programme, different mentor perceptions strongly determined how reflection is being taught to medical students. This may affect the students' professional identity formation. Training should enable mentors to reflect on their beliefs and mentoring style. Further research is needed on the effects of reflection in mentoring and on mentor selection.