English as a Lingua Franca (ELF) has not only generated a lot of interest among applied linguists and researchers, it has also attracted a great deal of attention among language teachers in recent years. What is particularly noteworthy is that ELF research has radically altered our way of thinking about language and the use of English in today’s globalized world (see, e.g., Dewey, 2013a, 2013b; Sung, 2013a, 2013b). It is therefore important for language teachers to understand more about ELF and its relevance for language teaching. In this interview, Martin Dewey, an expert in English as a Lingua Franca from King’s College, London, shares his ideas about the potential impact of ELF research on language teaching and teacher education. He previously taught English as a second language in Italy, Mexico, and the UK, and has trained language teachers on several pre-service and in-service programmes of teacher education. He is currently investigating ELF, and compiling a corpus of spoken ELF discourse for the purpose of describing and theorising current developments in the lexis, grammar, and pragmatics of English in lingua franca settings. He has published extensively on work in ELF, and is co-author with Alessia Cogo of Analyzing English as a Lingua Franca: A Corpus-driven Investigation (2012).