INTRODUCTION: Residency programmes are in transition to a framework for competency-based medical education (CBME). The intersection of CBME with transformational learning (TL) experiences and professional identity formation (PIF) - particularly within senior learners in transitional states - is unknown but important to understand in order to develop and implement strategies to support trainees' professional development. METHODS: Through inductive qualitative methods, we conducted semi-structured interviews (n = 22) of current trainees and recent graduates from adult cardiology residency training programmes within Canada to explore the impact of TL experiences on residents' professional growth and identity formation. Interviews were analysed using thematic analysis informed by TL theory. RESULTS: CBME did not appear to influence trainees' experiences of disorienting dilemmas and TL. Important clinical encounters and interpersonal relationships - in particular, those between mentor and mentee - shaped trainees' professional development as cardiologists ('enabling factors' for TL and PIF). 'Imposter phenomenon' was widely prevalent in our sample study population even among graduates who had already completed their training. Requisite elements for transformation (disorienting dilemmas, critical reflection, discourse and action) also contributed to PIF. DISCUSSION: TL experiences influenced PIF in senior learners but infrequently intersected with CBME
these experiences were more commonly prompted by disorienting dilemmas relating to clinical outcomes or interpersonal interactions independent of CBME-specific architecture.