This paper suggests that the professionalisation of interpreters in mental health care must be linked to the specific functions they have in their role as mediators and consequently to the identities they assume in this context. The involvement of a linguistic intermediary, a third person, brings additional complexity and plurality of frames to a setting that ordinarily includes two persons. Professionalisation, to my mind, implies sorting out and determining more precisely which function (or functions) the interpreter can have and will have in this kind of setting. In other words, professionalisation will concern the real functions and the desired functions of the linguistic intermediary. The paper distinguishes between four ways of viewing the role of interpreter, suggesting one of these – that of a culture and language broker more than that of a mere translator – to be developed for mental health care encounters specifically.