The use of English as the Medium of Instruction (EMI) in higher education is on the rise both globally and within Flanders, requiring lecturers to impart and students to construe knowledge in an additional language. Despite the growing prevalence of EMI, there is little empirical research into the interactional realities of EMI classrooms in Flanders. While much attention has been given to entry requirements, often focused on language proficiency benchmarks and testing, successfully navigating EMI classroom discourse demands more than linguistic proficiency alone. This project addresses the need for a deeper understanding of students’ interactional competence (IC) in EMI classrooms across the alpha, beta, and gamma sciences in Flanders. Employing authentic classroom data and a mixed-method approach, the study will examine students’ lexical proficiency, their use of conversational repair strategies, and their management of facework in classroom interactions. The project aims to develop a comprehensive model of IC, integrating content-related and interactional dimensions to offer a holistic view of the skillset required for effective participation in EMI classroom discourse, while also enabling the assessment of students’ IC. The findings will inform professional development for lecturers and support initiatives for students, enhancing readiness for the challenges of EMI classrooms in Flanders and contributing valuable insights to our understanding of the global EMI landscape.