Resumen: English as a Lingua Franca (ELF) is a linguistic paradigm that has been deeply researched for the last decades and that should be contemplated in the English as a Foreign Language (EFL) classroom. This necessary change is defended by scholars such as Björkman, Grazzi, Jenkins and Seidlhofer among others. ELF as a key element in today’s context of globalisation since English is considered the global language par excellence, then people need to learn it in order to achieve effective communication with both native and non-native speakers. People also need to leave their own culture aside and keep an open-minded cultural perspective while communicating with other users of English, acquiring multicultural competence. This dissertation contains a study of the concepts of ELF and multiculturality, and their implications in the Spanish secondary education EFL classroom. Research has been made through different methods, including observation, analysis of materials, a survey and an interview. After collecting both theoretical and contextual information using these methods, the innovation proposal composed by a didactic unit aimed to 4th ESO has been designed trying to adapt the activities both to the paradigm and to students’ necessities. This proposal attempted to provide secondary education students with tools and background knowledge that they may need in the future to communicate with other speakers of English in the international context. The case study represents an example of research on this field and, at the same time, contributes to the introduction of this new paradigm in the EFL classroom.