The present work is involved in synthesizing, characterizing, and evaluating the role of Er3+ ion on structural, optical, and thermal properties of 20CaO–10ZrO2–10Y2O3-30 B2O3-(30-x)SiO2-xEr2O3 (x = 0.3, 0.6, 1.0, and 1.5 mol%) compositions. The as-synthesized samples are characterized by various experimental techniques such as XRD, FTIR, Raman, UV visible spectroscopy, and DSC to study their suitability for optoelectronic applications. The density of glasses increases, whereas the molar volume decreases with the doping of Er2O3 in place of SiO2. The amorphous nature of the prepared samples is confirmed by the X-ray diffraction pattern. FTIR and Raman spectra confirm the presence of BO4 and BO3 structural units in the prepared glass samples. The UV–visible absorption spectra show 4G9/2, 4G11/2, 2G9/2, 4F5/2, 4F7/2, 2H11/2, and 4F9/2 transitions with the Er2O3 doping. The optical band gap increases from 3.25 to 3.61 eV, whereas the refractive index decreases from 2.33 to 2.24 with increasing doping of Er2O3, except for the SE-1.5 glass sample. The molar refraction decreases with Er2O3 doping. The glass transition temperature increases from 472 to 512 °C with Er2O3 doping in place of SiO2, except for the SE-1.5 glass. SE-0.3 glass shows the highest thermal stability, while SE-1.5 glass shows the lowest thermal stability. Therefore, these glasses can be considered for application in optoelectronics.