Introduction:Mentors in programmatic assessment support mentees with low-stakes feedback, which often also serves as input for high-stakes decision making. That process potentially causes tensions in the mentor-mentee relationship. This study explored how undergraduate mentors and mentees in health professions education experience combining developmental support and assessment, and what this means for their relationship.Methods:The authors chose a pragmatic qualitative research approach and conducted semi-structured vignette-based interviews with 24 mentors and 11 mentees that included learners from medicine and the biomedical sciences. Data were analyzed thematically.Results:How participants combined developmental support and assessment varied. In some mentor-mentee relationships it worked well, in others it caused tensions. Tensions were also created by unintended consequences of design decisions at the program level. Dimensions impacted by experienced tensions were: relationship quality, dependence, trust, and nature and focus of mentoring conversations. Mentors and mentees mentioned applying various strategies to alleviate tensions: transparency and expectation management, distinguishing between developmental support and assessment, and justifying assessment responsibility.Discussion:Combining the responsibility for developmental support and assessment within an individual worked well in some mentor-mentee relationships, but caused tensions in others. On the program level, clear decisions should be made regarding the design of programmatic assessment: what is the program of assessment and how are responsibilities divided between all involved? If tensions arise, mentors and mentees can try to alleviate these, but continuous mutual calibration of expectations between mentors and mentees remains of key importance.