The present work presents a study on the grafting of polyurethane onto chitosan in aqueous media. The effects of the amount of hydrophilic monomer on the water resistance of polyurethane were observed. Characterization of graft copolymers was performed by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), mechanical properties testing, and water resistance testing. TGA tests revealed that the thermal decomposition temperature of the copolymers increased significantly, being 34 ºC higher than that of pure gelatin while DSC measurements indicated that the glass transition temperature decreased by the introduction of polyurethane. Accordingly, the mechanical and anti-water absorption properties also proved to be enhanced greatly as evidenced by mechanical test and water absorptions data in which the copolymers containing 50% of polyurethane have highest elongation at break (325.6%), and lowest water absorption capacity (65%).