The development of the Internet and digital tools for interaction has enabled computer-mediated communication as part of the communicative approach to language learning and teaching. This creates affordances for learners of any target language from any location to communicate with each other, for example, through tandem language learning – that is, reciprocal two-way learning in dyads of two students with different first languages. Previous studies on tandem learning have mainly focused on the interaction between tandem partners in informal learning situations. In this study, we explore the teacher’s role in virtual classroom tandem applied to curriculum-based language teaching. The aim is to describe teachers’ engagement in interactional situations in the classroom, including the interplay between the physical classroom and virtual learning environments (VLEs). The data comprise video and screen recordings of teacher activities and interactions. The results reveal that virtual classroom tandem is a strongly student-centred approach where the teacher interaction during tandem lessons is notably narrower compared with tandem language learning based entirely on face-to-face meetings in a formal school context and in classroom instruction generally.