Poly(beta-hydroxy nonanoate)-polystyrene graft copolymers were prepared by the reaction of active polystyrene containing peroxide group with poly(beta-hydroxy nonanoate) at 80-degrees-C. Graft copolymers with a wide graft composition range depending on the amount of active polystyrene in the original mixture were produced and separated from the grafting product by fractional precipitation. NMR and IR spectra of the graft copolymers were containing the characteristic bands of the corresponding blocks. DSC curves of the graft copolymers had a large endotherm between 50 and 110-degrees-C.