Tree nuts are consumed as healthy snacks worldwide and are important economic crops. In this chapter, post-harvest processing technologies of tree nuts are discussed, with focus on the drying, disinfection, disinfestation, and downstream processing technologies (blanching, kernel peeling and roasting) for the control and preservation of product quality and safety. Almonds, walnuts, and pistachios are selected as the representative crops for the discussion. Current status, recent advances, and challenges in the scientific research, as well as in the industrial productions are summarized. Some new perspectives and applications of tree nut processing waste and byproducts (such as shells and hulls) are also introduced. The contents presented in this chapter will help both scientists and stakeholders to better understand the tree nut processing and provide technological recommendations to improve the throughput, efficiency, and sustainability of the processes, and preserve the quality and safety of the products.