This contribution gives an account of the results of an action research in which a task-based plurilingual programme was implemented with postgraduate students of Foreign Languages and International Business. Using a mixed-methods approach, combining questionnaire, interview and observation data, we sought to explore the degree to which the programme was accepted by the students; how it may have modified the representations they have of languages, language learning and plurilingualism; and how it contributed to their language development. The results of the study allowed us to identify the strengths, weaknesses, opportunities and threats involved in implementing a plurilingual programme for university students in a predominately monolingual area. The strengths include the theoretical validity of the programme design and the choice of the sample; the weakness inherent in the task design was the lack of necessity for collaborative learning techniques; the threats are sociocultural and contextual in nature in that French students generally do not appreciate teamwork and prefer to work individually; and the opportunities for further development lie in positive student representations of the social value of the programme, the intercultural dimension and their representations of language acquisition and plurilingualism which, for the majority, align with current theories.