The aim of this article is to reflect on the notion of authenticity and the use of authentic materials in English for Specific Purposes (ESP). In the professional context, ESP requires the use of specialized and authentic documents. Within the framework of a professional language for specific purposes program, this article firstly proposes a definition of the notion of authenticity before undertaking to examine various forms and applications of authentic documents or tasks. The author also proposes the conception of a new paradigm model for authenticity in the shape of a diamond, which is based on the synthesis of existing qualitative research studies. In this paradigm, authenticity and the language teacher are at the core of language teaching which brings together the learners (and their needs), the professional tasks and the authentic documents. In order to better appreciate the usefulness of authentic documents - such as video, sound, texts and photos - in the ESP context, the pedagogical approaches and criteria which are involved in choosing appropriate authentic materials and tasks are also shared. In addition, the article offers insight into current research on how to successfully integrate authentic materials into the ESP teaching environment through the use of film and television series. The critical research and findings of this article are of use to teachers of language (for specific purposes teachers) or language didacticians who wish to focus on the use of authentic documents when preparing their syllabus. Finally, this article shows that simplifying authentic documents is not always in the best interest of learners who are preparing for careers which require candidates who are professional and ready for employment.