© 2021 The Author(s)This study has been devoted to investigate the radiation shielding performance of epoxy-based micro and nano Bi2O3 and WO3 reinforced composites. While the research has been carried out by using experimental data and MCNP6 simulation for the micro-structured composites; the effect of nano Bi2O3 and WO3 particles addition on the radiation shielding property of epoxy has been discussed by using experimental data. While the gamma-ray spectroscopy experiments have been carried by using NaI(Tl) scintillation detector and Ba-133, Cs-137, and Co-60 sources, the MCNP version 6.2 code has been utilized for the simulation. The experimental and MCNP6 simulation results showed good consistency for both particle reinforcement and different incoming photon energies. Particle size effect investigation also indicated that for both kinds of dopant particles, the nano dopant is more successful in attenuating the intensity of incoming photons than the micro dopant even if they are used in the same percentages. In conclusion, it can be suggested that the micro and nano-structured composites having the highest Bi2O3 and WO3 contents have a considerable potential to shield the harmful effects of some of the diagnostic radionuclides utilized in nuclear medicine as well as the radiation imaging machines such as roentgen, mammography or PET scans.