Any discussion of transdisciplinary applied linguistics needs to engage with three central questions. First, while interdisciplinarity may allow for disciplines to stay in place and engage with each other, transdisciplinarity implies a space beyond or above disciplines. As a result, this paper has to consider whether applied linguistics is seen as a discipline (in which case it is not transdisciplinary) or whether it is seen as a transdisciplinary field of study (in which case it is not a discipline). Second, while applied linguists may engage with work from other fields – sociology, geography, philosophy, cognitive science are common examples – this does not necessarily mean that we engage with those fields as disciplines. Rather, the engagement with such work is often on the basis that relevant thinkers are engaging themselves with broader epistemic shifts. Such work may therefore be seen as having to do with epistemes rather than disciplines. Third, a focus on transdisciplinarity obscures broader concerns about unequal relations of knowledge production, particularly between North and South. If applied linguistics is to become a responsible field of work, it needs to engage with southern epistemologies. In order to do so, applied linguistic practices can be more usefully understood as temporary assemblages of thought and action that come together at particular moments when language-related concerns need to be addressed. This flexible account helps us see how applied linguistic practices are assemblages of different language-oriented projects, epistemes and matters of concern.