This chapter considers several approaches for integrating the observance of non-verbal behavior into task-based language teaching (TBLT) research to gain insight into the affective dimension of learners’ task performances. It begins with a review of previous investigations in applied linguistics that have used methods to capture learners’ non-verbal behavior as indicators of affect. Challenges that researchers face in attempting to use non-verbal behavior to gauge learners’ emotion in TBLT are then discussed. Finally, looking ahead with a multidisciplinary eye, the chapter outlines some future directions for researchers to consider as they attempt to investigate non-verbal behavior in TBLT.