This thesis explores the pedagogical incorporation of authentic texts in the teaching of Modern Greek as a second language, specifically to adults of lower level study, with regard to established practice in Modern Greek as L2 textbooks. It aims to, critically, approach all theoretical and didactic aspects of authenticity and to review the effectiveness of integrating authentic texts into language courses, by analysing the conditions which ensure their authentic usage. For these purposes, it makes a synthetic overview of the literature on the concept of authenticity in language teaching and it examines the use of authentic texts in the light of modern theories on second language acquisition and the responding teaching methodologies. In addition, it investigates the implementation of authenticity in eight Modern Greek as L2 textbooks. Finally, it proposes a threefold teaching model, whereby an authentic text is moved from the margins of language teaching to the forefront and is integrated in the main teaching body, as a referential and interactive framework, on a communicative, linguistic and cultural level.