In this work, electrical and structural properties of ferroelectric glasses and glass-ceramics from K_0.5Na_0.5NbO₃-SiO₂ doped with 0.5-1.0 mol%Er₂O₃ system have been investigated. The influent of Er₂O₃ dopant was also compared with the original glass. The K_0.5Na_0.5NbO₃ (KNN) powder was mixed with SiO₂ in composition of 75KNN-25SiO₂ and doped with Er₂O₃. Well-mixed powder was subsequently melted at 1300°C for 15 min in a platinum crucible using an electric furnace. The quenched glasses were then subjected to heat treatment at various temperatures for 4 h. From the study, KNN single phase in transparent glass was successfully prepared via incorporation method. The maximum Ԑ_r of about 360 at 10 kHz with a low tanδ of 0.07 could be obtained from the glass-ceramic sample of 75KNN–25SiO₂ doped 0.5 mol% Er₂O₃ and heat treated at 600°C. It can be seen that the higher percent of Er₂O₃ can lower the dielectric loss of KNN glass-ceramics. This interesting value suggesting the opportunity of using them in electronic applications in the future.