This article highlights the contribution of ethnography and qualitative sociology to the ethical challenges that frame the diagnosis of dementia. To illustrate this contribution, the paper draws on an ethnographic study of UK memory clinics carried out between 2012 and 2014. The ethnographic data, set alongside other studies and sociological theory, contest the promotion of a traditional view of autonomy; the limiting of the point of ethical interest to a distinct moment of diagnosis disclosure; and the failure to recognise risk and uncertainty in the building of clinical ‘facts’ and their communication. In addressing these specific concerns, this article contributes to the wider debate over the relationship between sociology and bioethics (medical ethics). At the heart of these debates lies more fundamental questions: how can we best understand and shape moral decision-making and ethics that guide behaviour in medical practice, and what should be the guiding ideas, concepts and methods to inform ethics in the clinic? Using the case of dementia diagnosis, this article illustrates the benefits of an ethnographic approach, not just for understanding this ethical problem but also for exploring if and how a more empirically informed ethics can help shape healthcare practices for the better.