BACKGROUND/AIM: We introduce the educational framework of 'threshold concepts' and discuss its utility in understanding the fundamental difficulties learners have in understanding ways of thinking and practising as occupational therapists. We propose that the relationship between occupation and health is a threshold concept for occupational therapy because of students' trouble in achieving lasting conceptual change in relation to their understanding of it. METHODS: The authors present and discuss key ideas drawn from educational writings on threshold concepts, review the emerging literature on threshold concepts in occupational therapy, and pose a series of questions in order to prompt consideration of the pedagogical issues requiring action by academic and fieldwork educators. RESULTS: Threshold concepts in occupational therapy have been considered in a primarily cross-disciplinary sense, that is, the understandings that occupational therapy learners grapple with are relevant to learners in other disciplines. In contrast, we present a more narrowly defined conception that emphasises the 'bounded-ness' of the concept to the discipline. CONCLUSION: A threshold concept that captures the essential nature of occupational therapy is likely to be (highly) troublesome in terms of a learner's acquisition of it. Rather than simplifying these learning 'jewels' educators are encouraged to sit with the discomfort that they and the learner may experience as the learner struggles to grasp them. Moreover, they should reshape their curricula to provoke such struggles if transformative learning is to be the outcome.