Proceeding from accepted shared definitions of applied linguistics that stress its practical, real-world orientation and instrumentality, this article seeks to move the focus from the interdisciplinarity that has been identified as the nexus of translation studies in the past to how its applied branches should systematically engage with an emerging transdisciplinary research paradigm. It argues that the shift can and will be a key factor, challenge and opportunity in the onward development of applied translation studies as it seeks to adequately address the situated realities of professional translation. The article reveals how transdisciplinarity, operationalised as action research, offers a viable framework for investigating, understanding and learning about what translators really do in working contexts and settings, with a view to identifying issues, improving practices, processes and performance, and ultimately transforming the profession for the good of those it employs and serves. In doing so, it considers approaches from cognitive translatology, based largely on a 4EA cognitive paradigm, and translatorial linguistic ethnography, where researchers are gradually but progressively going out into the field to explore and describe the complex socio-cognitive, socio-technical activity of translation in situ. After presenting a use case from a large-scale research project on translation ergonomics at the author’s home institution, the article puts forward a model for transdisciplinary action research in professional settings to guide the necessary transition from interdisciplinarity to transdisciplinarity. Such a model would allow professional processes and practices to be investigated, and the findings productively and transformatively applied, in the situated socio-cognitive and socio-technical contexts of translators’ workplaces - within, for, with and by the organisations that employ them.