The prominent increase in English medium instruction (EMI) in higher education has triggered the need for investigating EMI in practice in various contexts. Studies focusing on linguistic attitudes of EMI practitioners and learners are beginning to emerge but there are few studies exploring language-related issues in EMI practice. In response to this, this study investigates how language-related issues in EMI are conceptualized, approached and navigated. Data are drawn from document analysis, classroom observations and semi-structured interviews. The study finds that EMI courses were established without much presence of linguistic diversity and without an overt policy. Seemingly, EMI is treated as an invaluable commodity in the pursuit of internationalization. This puts the consistence and quality of EMI into question. It also finds that the practitioners have made polarized language decisions despite of an overall “English-only” preference. The polarized decisions lead to two modes of silence, namely “the English-only silence” and “the silence of English.” In addition, nativized Englishes were found to play in a key role in constructing EMI discourses, despite of a deeply-rooted belief in the Standard English ideology. This conflict between practice and perception reinforces the complexity of practitioners’ professional identity. Furthermore, it is also found that EMI, as an important way to pursue internationalization that celebrates heterogeneity, has a potential to circulate homogeneity. The findings are of significance for universities to (re)consider and (re)conceptualize language-related issues in EMI practice, and on the basis of this, design appropriate EMI curricula.