Polycrystalline sample of Ba4LiNb3O12 is synthesized in the temperature range of 1150°–1180°C by the conventional solid-state reaction method. A phase transition from cubic to hexagonal perovskite is observed around 1160°C. It is noted that hexagonal phase of Ba4LiNb3O12 obtained at 1180°C could be stabilized at a considerably lower temperature (∼950°C) with BaCu(B2O5) (BCB) added. BCB addition effectively improves the densification of Ba4LiNb3O12 ceramic and significantly affects the microwave dielectric properties. When 4 wt% BCB is added, a dense ceramic can be sintered at 950°C with a ɛr of 34.5, a high Q×f of 29 600 GHz, and a low τf of 12.4 ppm/°C. Moreover, BCB-added Ba4LiNb3O12 ceramics have a chemical compatibility with silver.