This article reports the influence of thulium oxide on gamma shielding parameters of (B2O3)0.2-x (TeO2)0.5 (Bi2O3)0.3 (Tm2O3)x glass system. The mass attenuation coefficient has been obtained by the WinXCom program, whereas the effective atomic number and the electron density have been calculated from a comprehensive and consistent set of formulas. Appreciable variations have been observed for all parameters by varying the chemical composition of the glass and the gamma photon energy. The theoretical results have shown that the addition of the rare-earth oxide, Tm2O3 into the glass system as the dopant attenuates more gamma irradiation and improves the radiation shielding properties of the glass system. The interactions between the photons and the glass materials have been explained by the Photoelectric Effect, Compton Scattering and Pair Production.