From the perspective that language and language usage consist of both speech and gesture (McNeill 1992, 2005, 2012) a number of studies have been conducted to examine gesture’s role in second language (L2) acquisition over the past thirty years. These studies have demonstrated the important role that gesture plays in both second and foreign language learning and teaching (for reviews, see Gullberg and McCafferty 2008; Stam 2013; Stam and McCafferty 2008; Stam and Buescher 2018; Tellier 2014). However, despite the growing interest in gesture and L2 learning and teaching among a number of researchers, the topic of gesture and its importance in understanding L2 acquisition is still not considered in most mainstream second language acquisition (SLA) studies. These studies on L2 learning and teaching have mainly focused on the analysis of speech production and seen gestures as peripheral to the process of learning and teaching. However, gestures play a very strong role in both learning and teaching because verbal language is only half of the picture (it provides a window only onto verbal thought and not imagistic thought), it is not always the most efficient medium for communication especially when there is an asymmetry in language proficiency between a learner and a teacher or a native speaker. L2 learning and teaching are interconnected and can be considered as two sides of the same coin: for instance, on the one hand, learners use gestures to scaffold their speech elaboration, and on the other hand, teachers use gestures to scaffold their speech comprehension by the learners. In addition, learners’ gestures indicate their language proficiency and comprehension of material, important aspects for teachers to take into consideration in their teaching. This chapter, although it focuses on adult learners, will provide evidence for why it is important to consider gestures in both L2 learning and teaching for all age ranges. It begins by defining co-speech gestures and pedagogical gestures. Next, it discusses how learners’ co-speech gestures show whether they are conceptualizing in their L1, their L2, or a combination of the two and to what extent different tasks affect the types of gestures learners produce. Then, it shifts to pedagogical gestures and illustrates how teachers engage their bodies in different ways in the classroom, the various functions of the gestures teachers use, and in what manner teachers vary their speech and gesture when engaging with non-native speakers, and what this tells us about teaching and communication.