The base glass (25 Bi2O3–25PbO-50B2O3) was doped with x = 0.5, 1, 1.5 and 2 moles % Er2O3 respectively. Glasses were prepared using the conventional melt-quenching method. Characterization was conducted using X-ray diffraction (XRD), glass density (GD), molar volume (Vm), differential scanning calorimetry (DSC), and UV-Vis spectroscopy. The XRD revealed the amorphous nature of the glass network , regardless of the Er2O3 content. The GD values exhibited non-monotonic behavior with increasing Er2O3 content, while the Vm showed a gradual increase. Bonding characteristics of the glasses under study have been calculated to clarify the effect of Er2O3 addition on the atomic glass structure. The DSC analysis showed a considerable increase in the Tg value for lower Er2O3 content followed by a sharp decrease. This may reflect the instability of the BO/NBO ratio in the glass matrix. In general, doping was found to increase the thermal stability of the glass. The measured optical properties exhibit a non-linear trend; the incorporation of 1.5 mole% of Er2O3 resulted in anomalous behaviors as a huge extension of the band tail to inside the forbidden gap occurred. On the other hand, the absorption characteristics revealed that glasses with 0.5 and 2% mole of Er2O3 displayed two localized band states inside the energy gap. These findings highlight the potential of Er2O3-doped Bi2O3-PbO-B2O3 glasses for advanced photonic applications.