The effects of ZnO addition on structure, microstructure and dielectric properties of (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3 ceramics (KNL–NTS) are investigated. Doping provokes phase segregation, evidenced by the appearance of different types of grains and a tetragonal tungsten–bronze secondary phase at high ZnO doping levels. A clear increase of ferroelectric–paraelectric and orthorhombic-to-tetragonal phase transition temperatures with ZnO content is observed. This produces a reduction of the room temperature piezoelectric constants due to the reduction of the tetragonality (c/a) ratio of the KNL–NTS structure.