Identity transformation is essential for young adults transitioning into a professional community of practice such as the teaching profession. In this study, the ten participants were in a teacher-education programme and completing their practicums, transitioning from identifying as a student to becoming a teacher. The research explored evidence of transformative learning and identity shifts as manifested in the participants’ written and spoken discourse. Datasets were reflective writings and semi-structured interviews, coded thematically. Seven of the ten resultant themes demonstrated characteristics of threshold concepts, critical concepts that transform understanding of a given domain; the other 3 themes represented professional praxes, important to dispositional readiness for teaching, but not characterisable as transformative, threshold knowledge. The findings contribute to: a nuanced approach to evaluating identity transformation and transformative learning in young adults; a keen understanding of identity transitions as integral to dispositional readiness for a professional domain; and further definition of the theoretical characteristics of threshold concepts, particularly as differentiated from praxes and dispositions.