Poly (ethyl methacrylate)(PEMA)/Casein nanoparticles with a well defined core shell structure having diameter 3.4 nm was prepared through direct graft copolymerization using small amount of benzoyl peroxide in water as catalyst at 80°C. The presence of casein micelles promoted the emulsion polymerization of the monomer and the particles stability. The graft copolymer and homo polymer were separated using chloroform as the solvent. The separated copolymer emulsion was immediately spread over a glass plate and was dried in air to form a bionanopolymer sheet. The polymer sheet sample was characterized using FTIR, TG-DTA and X-Ray diffraction studies. The scanning electron microscopic image of the nanoparticles showed that PEMA cores were coated with casein shells with well-defined core shell morphology. The conversion and grafting efficiency were also calculated.