This study focuses on disciplinary teachers' perceptions of International Classroom Affordances (ICA) during English-medium education in a multilingual university setting (EMEMUS) in Austria. The main aim is to generate a conceptual model grounded in the data that points to the perceptual mechanisms of disciplinary teachers involved in this particular case study. Findings leading to the ICA model suggest that teachers perceive ICA on four analytical levels (at the framing, reacting, appropriating and embracing stage). They were found to appropriate their classroom practices in line with the emergent action possibilities they were able to perceive. The sequential affordance-based perception process largely depended on their subjective grounds for action and reflection, but was also stimulated by the researcher in form of itineraries of transformation. Personal agency coupled with hardened internalised societal patterns and the positivist conception of institutional rules were identified as the biggest defordances in EMEMUS.