In this study, the glycolysis of polyethylene terephthalate was studied in presence of deep eutectic solvents as catalyst. In the glycolysis of PET, five different deep eutectic solvents were synthesized using different hydrogen bond donors and acceptors. Among the synthesized DESs, the most efficient catalyst was found to be DES formed by potassium carbonate and ethylene glycol. Glycolysis reaction was performed between PET and ethylene glycol. The effects of process parameters such as temperature, ratio of EG/PET and ratio of DES/PET were examined. The maximum yield for monomer product, bis(2-hydroxyethyl) terephthalate was observed as 88% at the reaction temperature of 180 degrees C, ethylene glycol/deep eutectic solvent ratio of 15 and deep eutectic solvent/polyethylene terephthalate ratio of 6.