The rapid increase in English medium instruction (EMI) in higher education has resulted in the need for a greater evidence base documenting EMI in practice spanning a range of settings. Studies of EMI focusing on linguistic issues are beginning to emerge but there are few comparative studies looking at multiple sites, levels and stakeholders. In response to this, the study reported here examined the roles of and conceptualisations of English and other languages in three EMI programmes in Thailand, Austria and the UK. A mixed-methods approach was adopted making use of a student questionnaire (N = 121) and interviews (N = 12) with lecturers and students, supported by documentary analysis and observations. Quantitative and qualitative analyses revealed diverse roles of English and other languages, various levels of recognition of multilingualism, and a sophisticated range of conceptualisations of language by stakeholders. In particular, English as discipline-specific language use emerged as a key concept, straddling language and content learning and teaching, as well as problematising simplistic divides between language and content. Furthermore, the complex understanding of the diverse roles of languages by participants offers a counter to perspectives of English in EMI as an unambiguous, monolithic entity.