The graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) by in situ polymerization method. The optimum high frequency (microwave) absorption was evaluated at X-band due to changes in the scattering parameters (determined by using a vector network analyzer). The slight improvement has been attained in gamma attenuation coefficient of the polymer nanocomposite by using gamma transmission technique. The addition of graphene nanoplatelets (2 wt%) resulted in a thermal improvement from 196.73 to 243.00 degrees C (with 5% weight loss) in TGA analysis. The graphene nanoplatelets provided an optimum decrease in scattering of the microwaves due to the elimination of the defects and the prevention of the agglomeration of the graphene nanoplates. The improvement of microwave absorption (between 8 and 12 GHz) suggested that the nanocomposite was a suitable candidate as a microwave absorbing material. This multipurpose nanocomposite has provided thermal stability and it has ensured the optimum gamma-ray and microwave absorption depending on the development of the structural properties. The development of these physical characteristics has enabled to improve the electrical conductivity as a result of the progress in the structural properties.