This chapter addresses the construct of emotion in task-based language teaching (TBLT). Drawing on existing research in educational psychology and language education, the first section provides a definition of emotion and discusses its relationship with cognition using Fredrickson’s (2004) Broaden-and-Build Theory. The second section then discusses the ways that emotion has been integrated into language education research and considers the role that learners’ emotions appear to play during second language task performance. The third section provides a critical discussion of how previous task-based research has examined emotion. This is followed by a review of recent research documenting the dynamic nature of emotions with the aim of providing a better understanding of how emotion can be integrated into TBLT research. The chapter ends with reflection questions and a recommended reading list for those who might want to further pursue the topic of emotion in relation to language task performance.