The influence of BaCu(B2O5) (BCB) on densification, phases, microstructure and microwave dielectric properties of ZnNb2O6–xTiO2 (x = 1.70–1.90) composite ceramics have been investigated. Undoped ZnNb2O6–1.8TiO2 ceramics sintered at 1200°C exhibit temperature coefficient of resonant frequency (τf) ~9.25 ppm/°C. When BaCu(B2O5) was added, the sintering temperature of the ZnNb2O6–1.8TiO2 composite ceramics was effectively reduced to 950°C. The results indicated that the permittivity and Q × f were dependent on the sintering temperature and the amounts of BaCu(B2O5). Addition of 3.0 wt% BaCu(B2O5) in ZnNb2O6–1.8TiO2 ceramics sintered at 950°C showed excellent dielectric properties of εr = 40.9, Q × f = 12,200 GHz (f = 5.015 GHz) and τf = +0.3 ppm/°C.