Prior research in Applied Linguistics has explored how teachers mobilise diverse resources in order to make connections between the students' out-of-school knowledge and experiences and the abstract content knowledge. Nevertheless, how teachers can transcend the boundaries of disciplinary knowledge by incorporating relevant content knowledge from other academic subjects to facilitate students' learning of new content knowledge is a topic that is under-researched in the field. Adopting translanguaging as an analytical perspective, this study examines how the creation of a translanguaging space can afford opportunities for an English-Medium-Instruction (EMI) teacher to connect content-related knowledge for supporting students' learning of new historical knowledge in EMI Western History classrooms. The data is based on a larger linguistic ethnographic project in a Hong Kong EMI secondary Western History classroom. Multimodal Conversation Analysis is used to analyse the classroom interaction data. The classroom interaction data is triangulated with the video-stimulated-recall-interviews that are analysed with Interpretative Phenomenological Analysis. This paper argues that a translanguaging classroom space can be ­created for activating students' prior learnt subject knowledge for ­supporting students' learning of new academic knowledge. Such a translanguaging space provides opportunities for classroom participants to not only engage in fluid language practices, but also encourages the teacher and students to bring in multiple epistemologies that help students understand new academic knowledge in a new classroom interactional context.