In this study, poly[methyl methacrylate-co-poly(ethylene glycol) methacrylate] (P(MMA-co-PEG500MA)) copolymers were used for catalase (CAT) immobilization. Firstly, P(MMA-co-PEG500MA) copolymers were synthesized by using different amount of methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (PEG500MA) monomers. The synthesized copolymers were characterized by different analysis techniques. Afterward, CAT enzyme was immobilized via physical adsorption method onto the P(MMA-co-PEG500MA) copolymers. P3 sample containing 1:1 (PEG500MA:MMA) monomer molar ratio was selected as model support because of exhibiting optimum surface porosity and thermal stability. A high immobilization yield (76%) was achieved under optimized conditions. The immobilized enzyme displayed improved tolerance towards pH and temperature changes. After immobilization, the optimum pH shifted from 7.5 to 7.0, whereas the optimum temperature remained unchanged at 35 degrees C. Immobilized enzyme showed good reuse potential and excellent storage stability. After 10 consecutive uses, immobilized enzyme maintained about 51.0% of its initial activity. Furthermore, free enzyme completely lost its initial activity after 4 weeks, while immobilized enzyme maintained approximately 65% of the initial activity at 25 degrees C. Approximately twofold decrease in Km was obtained which means that the affinity of enzyme to the substrate improved after immobilization. Finally, it can be concluded that the prepared P(MMA-co-PEG500MA) copolymer structure can be an ideal matrix for CAT immobilization.