The effect of LnAlO₃ (Ln = Nd, Sm) additives on the densification, phase evolution, microstructure and dielectric properties of BaO-Nd₂O₃-5TiO₂ (BNT5) ceramics was investigated. The LnAlO₃ (Ln = Nd, Sm) had greatly influence on the densification behavior of the BNT5 ceramics and the grain sizes of BNT5 ceramics could be effectively refined by LnAlO₃ additive. The microstructure of BNT5 ceramics was transformed from quasi-rectangular grain to columnar grain while the content of LnAlO₃ was increasing. The dielectric constant (ε_r) and the temperature coefficient of resonant frequency (τ_f) were reduced with the increase of LnAlO₃ content, whereas the Q×f values showed a non-linear behaviour with LnAlO₃ content increasing. The BNT5 ceramics doped with 12.5 wt% SmAlO₃, sintered at 1320°C for 4 h, had the excellent dielectric properties of ε_r = 62.78, Q×f = 11108 GHz and τ_f = -1.55 ppm/°.