Methoxypolyethylene glycol (mPEG) covalently bound to the surface of human red blood cells (hRBCs) has been shown to decrease immunological recognition of hRBC surface antigens. However, there is an increasing shortage of hRBC donations, thus making the supply of hRBCs scarce and expensive. The goal of this study is to similarly PEGylate the surface of bovine RBCs (bRBCs), with the aim of reducing the demand on human blood donations needed for blood transfusions. This study investigates the feasibility of modifying the surface of bRBCs with the 20 kDa succinimidyl ester of methoxypolyethylene glycol propionic acid (SPA-mPEG) for use as a potential blood substitute. It was found that SPA-mPEG reacts with bRBCs in a dose dependent manner as the mass of conjugated SPA-mPEG on the bRBC surface increases with increasing initial SPA-mPEG concentration. The overall oxygen binding affinity of PEGylated bRBCs was moderately increased with increasing initial SPA-mPEG concentrations up to 6 mM when reacted with bRBCs at a hematocrit of 12%. Control bRBCs exhibited a P50 (oxygen affinity) of ~28 mmHg, while bRBCs reacted at 6 mM SPA-mPEG exhibited a reduced P50 ~21 mmHg. Oxygen transport simulations modeling the oxygen distribution within the capillary and tissue space, were conducted to insure that PEGylated bRBCs were capable of delivering oxygen to tissues. These simulations showed that SPA-mPEG conjugated cells could still transport vital oxygen to pancreatic islet tissues and maintain the tissue's O2 tension above hypoxic levels even under extreme conditions. PEGylated bRBCs reconstituted to a physiological hematocrit of 40% exhibited viscosities on the order of ~ 3 cp, similar to hRBCs at the same hematocrit. Finally, PEGylated bRBCs exhibited similar flow characteristics in a glass capillary indicating bRBCs retain most of their deformability with mPEG modification. Taken together, the results of this study demonstrate the success of PEGylating bRBCs to yield modified cells with oxygen binding, transport and flow properties similar to that of hRBCs.