Numerous residents suffer from stress, anxiety, which may be acutely exacerbated by stressful situations such as being on call. When confronted with uncertainty situations, residents experience a mismatch between their theoretical knowledge and their clinical reasoning skills. In a previous study we observed high levels of cognitive weariness and anxiety in residents being on call in the paediatric emergency department, and the reduction of their cognitive weariness by training clinician-educators in the supervision of clinical reasoning.We sought to inform the findings of our previous research by exploring in depth the experience of on-call residents in the paediatric emergency department, including: the factors that impact their well-being, and how supervision of their clinical reasoning might change it.We performed a qualitative study using semi-structured interviews. We interviewed medical residents who were on call in the emergency department, mentored by supervisors who had received specific training in the supervision of clinical reasoning.The findings revealed two opposing profiles of how residents experience being on call and having their clinical reasoning supervised. First, there were those who expressed marked discomfort, characterized by anxiety, a strong need for supervision, a fear of being judged by the supervisor, and a major impact of physical fatigue. Residents with this profile seem to be at risk of developing burnout. The second profile expressed little unease, had a sense of self-efficacy, a feeling of personal competence, a high level of self-confidence, greater tolerance of uncertainty, and little difficulty with making decisions.Clinical experience alone may not linearly move residents from basic to advanced reasoning. Targeted supervision techniques can identify these difficulties and provide remediation strategies. In emergency departments, lack of experience and few operational scripts hinder non‑analytical reasoning, requiring systematic data analysis and high working‑memory capacity. The study links working‑memory load to cognitive fatigue, a burnout component, and suggests that improving reasoning scripts could reduce anxiety and burnout.Supervision of clinical reasoning based on questioning techniques seems to participate to promote development towards second profile, with greater tolerance of uncertainty, ease with decision-making, and a reinforced sense of belonging to a team.