This study investigates the effects of La2O3 on the mechanical, thermal, and physical characteristics and the ability of bismuth germinate glass with different compositions to protect against radiation. The glasses included ZnO, Na2O, Bi2O3, GeO2, and different concentrations of La2O3 (between 0 and 20 mol%). The glass density substantially increased from 3428 kg/m³ to 4412 kg/m³ as the concentration of La2O3 increased. This observation underscores the considerable influence of La2O3 on densification, which can be attributed to its higher coordination number and molecular weight. In addition, bridging oxygen atoms reduced the molar volume from 60.2 to 57.8 × 10−6 m3. This decrease suggests the synthesis of oxygen atoms, which increase the glass transition temperature from 536 to 573 K, improving the glass's thermal properties under investigation. As the amount of La2O3 increased, the ultrasonic velocity measurements indicated an increase in longitudinal and shear velocities from 3192 to 3611 m/s and 1884–2185 m/s, respectively. Longitudinal and shear ultrasonic velocity measurements can be utilized to determine the elastic moduli, Poisson's ratio, and Debye temperature. Correlations between these results and theoretical models highlighted the strengthening effect of La2O3 on the glass structure. Another important study area was radiation shielding efficiency, which showed that higher La2O3 content improved photon blocking. The study showed the potential of La2O3-enriched glasses in applications needing radiation protection by looking at the effective atomic number and neutron shielding. Overall, adding La2O3 strengthens the characteristics of bismuth-germinate glasses, increasing their suitability for certain applications in radiation-exposed areas. •La2O3-doped bismuth-germanate glasses synthesized.•Improved mechanical and shielding properties.•Empirical and theoretical validations were conducted.•Outperforms heavy-weight concrete in shielding.