The purpose of this study is the making of multilayer type I capacitors composed of ZnNb2O6 co-sintered with silver electrodes. In order to lower the sintering temperature, we have mixed three commercially available glass frit powders with ZnNb2O6. The sintering behaviours were studied by thermomechanical analysis (TMA). Two additives allowed us to sinter ZnNb2O6 at 900 °C. The sintered ceramic pellets show a type I dielectric behaviour close to the one of pure ZnNb2O6 (e.g.: dielectric constant around 22, resistivity above 1012 Ω. and dielectric losses lower than 10−3). Ceramics were co-sintered with Ag in order to estimate Ag diffusion behaviour. One composition, ZnNb2O6+5 wt% (B2O33ZnO3SiO2) glass frit can be co-sintered at 900 °C with Ag electrodes and leads to type I dielectric properties.