(1−x)ZnNb2O6·xTiO2 ceramics were prepared using both anatase and rutile forms of TiO2. At a composition of x= 0.58, a mixture region of ixiolite (ZnTiNb2O8) and rutile was observed and the temperature coefficient of resonant frequency (τf) was ∼0 ppm/°C. We found that although ɛr and τf were comparable, the quality factor (Q×f, Q≈ 1/ tan δ, f= resonant frequency) of 0.42ZnNb2O6·0.58TiO2 prepared from anatase and rutile was 6000 and 29 000, respectively. The origin of the difference in Q×f of both samples was investigated by measuring electrical conductivity and by analysis of the anatase–rutile phase transition. The anatase-derived sample had higher conductivity, which was related to the reduction of Ti4+. It is suggested that the increase of dielectric loss originates from an increase in Ti3+ and oxygen vacancies due to an anatase–rutile phase transition.