PurposeClinical supervisors hesitate to report learner weaknesses, a widely documented phenomenon referred to as “failure to fail.” They also struggle to discuss weaknesses with learners themselves. Their reluctance to report and discuss learner weaknesses threatens the validity of assessment‐of‐learning decisions and the effectiveness of assessment for learning. Personal and interpersonal factors have been found to act as barriers to reporting learners’ difficulties, but the precise role of the resident–supervisor relationship remains underexplored, specifically in the emergency setting. This study aims to better understand if and how factors related to the resident–supervisor relationship are involved in assessment of and for learning in the emergency setting.MethodsWe conducted a qualitative study, using semistructured interviews of 15 clinical supervisors in emergency medicine departments affiliated with our institution. Transcripts were independently coded by three members of the team using an iterative mixed deductive–inductive thematic analysis approach. The team then synthesized the coding and discussed analysis following guidelines for thematic analysis.ResultsParticipating emergency medicine supervisors valued resident–supervisor relationships built on collaboration and trust and believed that such relationships support learning. They described how these relationships influenced assessment of and for learning and how in turn assessment influenced the relationship. Almost all profiles of resident–supervisor relationships in our study could hinder the disclosing of resident weaknesses, through a variety of mechanisms. To protect residents and themselves from the discomfort of disclosing weaknesses and to avoid deteriorating the resident–supervisor relationship, many downplayed or even masked residents’ difficulties. Supervisors who described themselves as able to provide negative assessment of and for learning often adopted a more distant or professional stance.ConclusionsThis study contributes to a growing literature on failure to fail by confirming the critical impact that the resident–supervisor relationship has on the willingness and ability of emergency medicine supervisors to play their part as assessors.