Electrospun nanofibers are a class of nanomaterials appropriate for various applications, such as smart films, filter membranes, catalytic supports, energy generation modules, conversion and storage, photonic and electronic sensors, biomedical scaffolding, and other devices. Electrospinning is a flexible and versatile technique for processing nanofiber materials; it consists of an electrohydrodynamic process in which liquids are electrified to create a beam and then stretched into fibers. The basic set up for electrospinning is relatively simple and, therefore, accessible to almost every laboratory. The main components are a high voltage DC power supply, a syringe device, a spinner, and a conductive collector. Due to the increasing consumption of polyethylene terephthalate-based products and their waste disposal issue, increasing environmental concern has led us to transform this waste into valuable products. This chapter focuses on the research studies of electrospun waste polyethylene terephthalate to produce nanofiber, applied in a different application.