Pancreatic islet transplantation is one of the most promising strategies for patients suffering from type 1 diabetes mellitus, but several therapeutic immunosuppressive medications must be administered to protect transplanted islets in the long-term and these expose patients to the risk of serious complications. Therefore, it is necessary to attenuate or eliminate the usage of immunosuppressant. Here, we introduce pancreatic islet PEGylation technique on the surface of islets to reduce immunogenicity of transplanted islets, thereby reducing dosage of immunosuppressive medicines. In addition, various strategies are tried to show the synergistic effect of the conjugated PEG molecules on the prevention of immunoisolation and induction of immune tolerance. This review critically addresses various insights developed in each individual strategy.