This thesis seeks to encourage an anthropology of psychology through an ethnographic account of evidence-based psychological therapy in the United Kingdom. It examines the ‘Improving Access to Psychological Therapies’ (IAPT) service established in 2008 as part of the National Health Service (NHS) and is based on 18 months of fieldwork conducted between 2016 and 2018 amongst mental health professionals and therapists-in-training. Through the invention of IAPT, 'Cognitive Behavioural Therapy' (CBT) and other cognate therapies such as 'Mindfulness' have become a hallmark of ‘evidence-based’ psychological healthcare. This research takes up the question of their acclaimed scientific status and asks how, and with what effects, psychological therapies have become conceivable and workable within the framework of evidence-based medicine (EBM). Divided into six chapters, the thesis offers a series of ethnographic reflections on some of the effects of the institutionalisation of evidence-based psychological therapy and the scientific persuasions that have made it possible. This research thus investigates the principles underlying psychological therapy, how they are conveyed through training and conferences, and how practitioners make sense of them in their everyday work. It examines some of the histories and logics that underscore the invention of IAPT, how psychological therapies align with dominant discourses in biomedicine concerning treatment and evidence, and some of the assumptions concerning ideas of selfhood that are implicit in them. We will see how professionals acquire particular skills and sensitivities in order to become therapists, how within specific professional contexts they debate and disagree with each other, yet also how they produce certain forms of critique and contextualisation familiar to social scientists. The ethnography shows that whilst psychological therapies – from ‘CBT’ to ‘Mindfulness’ – have become recognised as effective interventions for a range of mental health problems, they have also generated their own empirical tensions and uncertainties. We follow these ethnographic realities as we move from some of the ambitions and problems of the IAPT service to the contexts of research, education and training of therapists. The thesis argues that the epistemic success of CBT as the benchmark model of psychological healthcare in the UK rests on a persuasive, recursive move: CBT introduces accountability and measurement at the heart of its proposed vision of mental health – enacted through particular therapeutic practices of self-reporting and self-inspection – and this, in turn, enables it to demonstrate its value and validity in the terms set by the conventions of ‘evidence-based’ practice. As a result, psychotherapeutic care has been reconstituted as a highly manualised, standardised and quantifiable intervention. It is the quest for objectivity and scientific validation that requires psychological therapy to be enacted as an object of scientific testing and accountability by way of rendering the human subjecthood at the core of its practice amenable to measurement and intervention. Such an ambition is not new in psychology, as we shall see, but it has been revivified in new and interesting ways through the promises and persuasions of evidence-based psychological therapy. The thesis thus contributes to anthropological studies of scientific epistemologies and therapeutic practices and suggests a way of treating ethnographically common psychological realities, including those found in the conceptual worlds of anthropologists.