Mental health professionals and clinical students face uncertainties when attempting to provide care and support to diverse patient populations, such as immigrants, refugees, and their children. These uncertainties may result in misunderstandings and failures to respond to the needs of patients. Uncertainties are due to the limits of clinical knowledge among clinicians and in the field (Fox, 1957), and may be heightened in encounters with patients who speak other languages, whose living conditions are extremely unstable, or who have different ways of expressing their experience of disorder. Broadly, health professionals and students attempt to attenuate these uncertainties by pursuing training in cultural competence or cultural sensitivity, so that they may learn how to better support diverse patients. Cultural competence training in France has been critiqued for advancing essentialist notions of culture and for not respecting universalism and assimilation, which guide the provision of public services. These critiques have prompted clinicians to emphasize the development of the ability to decenter from one’s own cultural representations in order to recognize those of others, and become more self-reflexive (Larchanché, 2010; Moro, 1998; Moro, 2002; Sturm, 2005; Sturm, Heidenreich, & Moro, 2008). The emphasis on decentering reflects broader trends that challenge notions of expertise and competence in cultural sensitivity training, and that promote the embrace of uncertainty and the development of a self-aware, “ethical self” (Shaw & Armin, 2011: 244). Leaders in the field of psychiatrie transculturelle, or transcultural psychiatry, have suggested that decentering is an essential practice for health professionals, but is difficult to learn and requires rigorous training and supervision (Moro, 1998). Drawing on twenty-two months of fieldwork, this dissertation examines how clinical students in psychology and psychiatry learned to address uncertainty and develop decentering practices through apprenticeship (Lave and Wenger, 2009) under the supervision of culturally sensitive clinical psychologists and psychiatrists in mental health settings for immigrant, refugee, and non-francophone patients in Paris. The supervisors in these settings encouraged apprentices to unlearn the rigid modes of thinking and forms of expertise they acquired in their training in psychiatry and psychology. A closer examination of apprentices’ activities within these settings reveals that while supervisors promoted the development of openness, flexibility, and the acceptance of uncertainty, apprentices were made to perform roles of diversity in front of patients, simplify and systematize complex patient information into manageable forms, and discipline their speech to adhere to the institutional frameworks of these settings. While intended to train apprentices to minimize or accept uncertainty, these practices provoked new forms of uncertainty. I argue that the divide between the perspectives of apprentices and their supervisors is a rich and crucial site of analysis, as apprentices advanced more inclusive, cosmopolitan, and intersectional ways of conceptualizing cultural diversity in therapeutic interactions. Moreover, I contend that the inconsistencies in practice and rigid pedagogical styles of supervisors prompted apprentices to develop selective and heterogeneous styles of practice following their apprenticeship. This dissertation thus contributes an anthropological lens to the transmission of expertise with an eye towards how cultural sensitivity is learned and uncertainty is addressed through experience.