The present study reveals the effect of LaScO₃ content on the structural, dielectric, and piezoelectric properties of perovskite structured (1 - x)(K_0.5-Bi_0.5)TiO_3–xLaScO₃ (named as KBT–LSO) (x = 0–0.40) ceramics. A decrease in tetragonality and an increase in cubic phase fraction with LaScO₃ doping were observed in Rietveld refinement of synchrotron X-ray diffraction (SXRD) data. Room temperature dielectric constant (ε_τ) was found to improve in KBT–LSO solid solution. A continuous decrement in temperature of dielectric maxima (T_m) from 360 °C for x = 0.00 to 87 °C for x = 0.40 of LSO-doped KBT sample (at 1 MHz) was noticed. Highly diffuse dielectric anomaly and increasing relaxor behavior were observed with increased LSO doping content. The greater value of depolarization temperature (T_d ~ 310 °C) compared to normal to relaxor ferroelectric transition (T_F-R ~ 255 °C) for a 2% LSO-doped sample signifies a nonergodic relaxor state in the system. The impedance spectroscopy suggested improved DC resistivity with LSO incorporation in KBT lattice. The activation energies were obtained in the ranges 0.98 ± 0.03 eV to 1.50 ± 0.02 eV using Arrhenius equations which signifies the reduction in oxygen vacancies due to LSO doping. The current (I)–voltage (V) plot confirmed the decrement in room temperature DC conductivity (σ_DC) with LSO doping concentration.