Methyl methacrylate grafted natural rubber (NR) prepared by free radical polymerisation of methyl methacrylate in NR latex was irradiated to high energy radiation. Their structure and molecular dynamic changes during exposure to high energy radiation were investigated by dynamic mechanical analysis and solid state nuclear magnetic resonance spectroscopy (NMR). The changes of glass transition temperature and tan delta(max) with different radiation doses are reported. The effect of the radiation dose on tan delta peak width, tan delta(max) and area under the tan delta curve are used to understand the miscibility and damping properties of the irradiated rubbers. This data was also used to calculate the radiation chemical yields of crosslinking, G(X), and scission, G(S). Solid state C-13 NMR measurements were carried out to determine the several relaxation time parameters; rotating frame and laboratory frame proton and carbon relaxation times. Cross polarisation times and carbon relaxation times were interpreted based on the changes in the molecular motion. Proton relaxation times were interpreted based on the heterogeneity of the matrix. Results confirmed the disappearance of the interfacial region and phase separation during irradiation.