Transparent waste soda-lime glass (SLS) reinforced with Nb2O5 (0.005, 0.05, and 0.5 wt%) was successfully synthesized using a conventional melting technique for gamma-radiation attenuation applications. The synthesized glass series (RG, RGN1 to RGN3) were then subjected to some physical, optical, and radiation shielding measurements. The physical measurements and computations showed that the increasing content of Nb2O5 increased glass density (rho(glass)), molar volume (V-m), and oxygen molar volume (OMV), however, decreased oxygen-packing density (OPD). Moreover, several optical parameters, such as the refractive index (n), dielectric constant (epsilon), and metallization criterion (M), were evaluated. One can say that the optical and physical properties can be improved owing to the addition of Nb2O5 in waste SLS glass. The gamma-ray transmission method was utilized to measure the linear attenuation coefficient (LAC) for the fabricated RGN glass series for gamma-photon energies 0.662, 1.173, and 1.332 MeV emitted from Cs-137 and Co-60, respectively. The accuracy of the obtained results was tested by comparing the experimental data with those simulated by MCNP-5 and those computed theoretically by XCOM. The obtained results showed agreement between the experimental measurements, simulated, and theoretical evaluations. We found that the photons with energy of 0.662 MeV have a lower penetration power. Thus, the LACs are higher at 0.662 MeV for all synthesized glass samples. The LAC values at 0.662 MeV were between 0.1849 and 0.2253 cm(- 1) for the glass samples RG and RGN3. The LAC results depicted a significant relationship between the chemical composition and the synthesized glass series' attenuation coefficients. The LAC's measured values were enhanced with the insertion of the niobium pentoxide (Nb2O5) contents. The half-value layer (HVL, increment (0.5)) was calculated for the synthesized glass series based on the measured LAC. The thinner increment (0.5) layers were achieved at 0.662 MeV and ranged between 3.077 and 3.748 cm for the glasses coded as RGN3 and RG, respectively, while the thicker increment (0.5) layers were found at 1.332 MeV and changed in the range of 4.306-4.914 cm. The influence of the Nb2O5 doping ratio was examined, and we found that the values of the increment (0.5) layers become thinner as the Nb2O5 doping ratio increases.