The objective of this study is to explore how the replacement of barium oxide (BaO) by bismuth oxide (Bi2O3) affects the optical, structural and gamma rays shield ability of borate glasses. To accomplish this, a series of borate-based glasses was fabricated according the chemical formula 60B2O3 + (40-x) BaO + xBi2O3, where 0 < x < 10 wt.%. X-ray diffraction confirmed that an amorphous phase was present at all fabricated glasses. Thermal analysis indicated that Bi2O3 could serve as a glass modifier for all values of x greater than zero. Furthermore, the optical absorption profile showed that the samples had a greater absorption rate as x increased within the 1–4 eV photon energy range, with only minor fluctuations beyond 4 eV. Monte Carlo simulation demonstrated that increasing the concentration of Bi2O3 led to an increased radiation-absorbing capacity, where the linear attenuation coefficient of the fabricated glasses enhanced by 26% from 74.48 to 94.17 cm−1 at gamma ray energy of 0.015 MeV. Simultaneously, the half value thickness for the fabricated glasses reduced from 3.99 to 3.73 cm, raising the Bi2O3 concentration between 0 and 10 wt.%, respectively. These results indicate that adding Bi2O3 to boron oxides can significantly improve shielding the ability of the material to against gamma rays, alter the glass samples, and potentially be cost-effective. This study could lead to faster synthesis processes for glass modifiers, with important implications for designing and producing materials to shield against harmful gamma rays in industrial and medical applications.