Studies related to dissolution-based recycling using deep eutectic solvents (DESs) are still scarce. Therefore, this chapter covers the dissolution mechanism of polymer–solvent systems, particularly focusing on DES-based dissolution of PET and the subsequent processes after dissolution. PET recycling via DES-catalyzed glycolysis, the practicality of dissolution-based recycling for plastic waste, and the associated challenges are also discussed in this chapter. Suitable solvents must be used to ensure that only one polymer remains in the solid state at each step. It is also important to note that the selected solvents may vary depending on the plastic composition. Solvent-based recycling can serve as an alternative to mechanical and chemical recycling. In dissolution-based recycling, DESs act either as solvents or catalysts, providing nucleophilic sites for solvolysis and facilitating the development of synthetic processes that are more biocompatible and environmentally friendly compared to traditional solvolysis methods for plastic materials. Furthermore, their application enables mild depolymerization reaction conditions, reducing energy requirements without compromising performance.