CONTEXT: Several recent studies have documented the fact that, in considering feedback, learners are actively making credibility judgements about the feedback and its source. Yet few have intentionally explored such judgements to gain a deeper understanding of how the process works or how these judgements might interact to influence engagement with and interpretation of feedback. Using the educational alliance framework, we sought to elaborate an understanding of learners' credibility judgements and their consequences. METHODS: Using constructivist grounded theory we conducted semi-structured interviews with psychiatry residents. We used a theoretical sampling approach that invited participants with diverse scores based on a previously published feedback survey and an investigator-developed educational alliance inventory. Consistent with the principles of grounded theory analysis, data were collected and analysed in an iterative process to identify themes. RESULTS: Participants depicted themselves as actively contemplating feedback and considering it thoughtfully in light of complex judgements regarding their supervisor, the relationship with their supervisor and the larger context in which the feedback interactions were occurring. These judgements focused on the supervisor's credibility both as a clinician and as a partner in the educational alliance. The educational alliance is judged by trainees in relation to the supervisor's engagement as an educator, commitment to promoting growth of residents and positive attitude toward them. CONCLUSIONS: Our findings suggest that credibility is a multifaceted judgement that occurs not only at the moment of the feedback interaction but early in and throughout an educational relationship. It not only affects a learner's engagement with a particular piece of feedback at the moment of delivery, but also has consequences for future engagement with (or avoidance of) further learning interactions with the supervisor. These findings can help medical educators develop a more meaningful understanding of the context in which feedback takes place.