Ba₅Nb₄O₁₅ powders were synthesized by molten-salt method in NaCl–KCl flux at a low temperature of 650–900 °C for 2 h, which is lower than that of the conventional solid-state reaction. This simple process involved mixing of the raw materials and salts in a certain proportion. Subsequent calcination of the mixtures led to Ba₅Nb₄O₁₅ powders at 650–900 °C. XRD and SEM techniques were used to characterize the phase and morphology of the fabricated Ba₅Nb₄O₁₅ powders, respectively. After sintering at 1,300 °C for 2 h, the densified Ba₅Nb₄O₁₅ ceramics with good microwave dielectric properties of ε_r = 39.2, Q × f approximated as 27,200 GHz and τ _f  = 72 ppm/°C have been obtained.