Despite the emerging interest in (health) platforms, there is limited research on their role in shaping professional work. Existing research has primarily focused on how platforms generate new forms of work, such as micro-tasking and crowdworking. There is limited understanding, however, about what forms professional work might take place on platforms, and, perhaps more importantly, how platforms can establish professionalism, primarily in contexts where this is under-developed or -valued. Our paper illustrates how this can be achieved drawing on a longitudinal qualitative study of a non-profit platform that is dedicated to delivering free online health education in post-conflict countries. The paper discusses four mechanisms through which platforms make up professionals: standardisation of clinical practice; normalisation of professional behaviour; development of medical knowledge; and inculcation of values. It then aims to discuss the paradoxical bureaucratic effects platforms may have as they enable those mechanisms and the potential colonising consequences they may engender.