In this chapter, we explore the use of Augmented Reality (AR) and Virtual Reality (VR) in geometry courses for teachers. There is increasing use of AR and VR technologies, such as AR and VR goggles, in K-12 schools, providing new opportunities for learners to interact with geometry in three-dimensional (3D) environments. These opportunities lead to a need for teacher training related to these technologies. Further, AR and VR technologies offer teachers opportunities to understand geometry concepts themselves more deeply. We connect AR/VR technologies to theories of embodied cognition, as well as to the interaction with geometric objects that AR/VR allows. This chapter presents illustrative examples and observations from the GeT courses, highlighting how teachers engage with properties of 2D and 3D shapes in AR/VR and collaborate with others around dynamic simulations. We emphasize the potential of these environments to enhance geometry learning by allowing learners to manipulate shapes and observe real-time changes in measurements and figures. Further, we focus on the affordances and constraints of AR/VR for classroom use, what teachers can learn about using AR/VR technology in their classroom in GeT courses, and what teachers can learn about geometry from AR/VR. Particularly, we discuss deriving and explaining geometric arguments through teacher experiences with AR/VR technologies and provide recommendations for geometry teachers and teacher educators. [This chapter will be published in: "The GeT course: Resources and Objectives for the Geometry Courses for Teachers," A. Brown et al., Mathematical Association of America.]