The present chapter explores the conceptual foundations of Foreign Language Enjoyment (FLE) and Foreign Language Anxiety (FLA) within the context of Second Language Acquisition (SLA). The body of the chapter is divided into two main parts. The first one coalesces around foreign language enjoyment, its conceptualization, components, and sources, and beneficial effects on the learner. It presents the crucial role of enjoyment in foreign language learning which is grounded on the Fredrickson’s Broaden-and-Build Theory of Positive Emotions (2001), as well as the Control-Value Theory of Achievement Emotions (Pekrun and Perry in International handbook of emotions in education. Routledge/Taylor & Francis Group, 2014; Pekrun et al., in Emotion in Education. Academic Press, 2007). The second part of the chapter focuses on the most frequently studied emotion in the field of SLA, namely foreign language anxiety. It delineates its conceptual roots, causes and effects on the FL learning process. The final part of the chapter presents possible interrelations between the two constructs under investigation. It is highlighted that while FLA can significantly hinder language learning by reducing cognitive capacity and impairing information processing, FLE serves as a motivating force that enhances learners’ engagement and receptiveness to language input.