English has become a language commonly used in fields such as business, diplomacy, or tourism. It is also a medium which enables the transfer of knowledge and the development of ideas in science and education. Scientists and undergraduates can nowadays pursue their research and studies at laboratories and universities all over the world using English as the language of the educational process. Thus, they access knowledge in their respective fields through English, and this applies also to learning other languages. Learning a foreign language using English poses various challenges, starting from the learners’ level of English over to the influences that English can have on the process of acquisition. Also, learners can have beliefs about learning the other language (L3) which differ from beliefs they have about learning English. This set of ideas, attitudes and opinions could have an impact on how students learn L3. This paper explores the beliefs about, and motivations for, language learning among a small group of Erasmus students in the International Relations Programme at the Faculty of Social Sciences, Masaryk University, Brno. The students, who have various ethnic origins and language backgrounds, took part in a thirteen-week course of French for Beginners, taught in English by a Czech teacher. Most students were complete beginners, but others already had basic knowledge of French, as the entry questionnaire had shown. This course of French for specific purposes (diplomacy) covered the first three units of an A1-A2 textbook called Objectif Diplomatie: Le français des relations européennes et internationales. At the end of the course, learners completed a questionnaire in English. This research gauges the role of English as a medium in learning French at a beginner’s level and investigates students’ perceptions of the accuracy and the difficulty of learning French through English. Avoiding any generalisations, the study reports group-specific results with a view to showing whether, and to what extent, students conform to other research findings in the areas of learner beliefs and motivations in English-medium language instruction.