Abstract The effect of Zn2+ substitution on the structure and microwave dielectric properties of Li3Mg2NbO6 ceramic was investigated. The compositions of Li3(Mg1−xZnx)2NbO6 (0≤x≤0.1) ceramics were prepared by the solid-state reaction method. The phase structure, microstructure and microwave dielectric properties of Li3(Mg1−xZnx)2NbO6 ceramics were analyzed via an X-ray diffraction, a scanning electron microscope as well as a network analyzer. All samples sintered at 1080–1240°C for 4h remained a single orthorhombic structure, which could be indexed according to the Li3Mg2NbO6 phase (JCPDS-PDF #86-0346). The microwave dielectric properties of Li3(Mg1−xZnx)2NbO6 ceramics exhibited significant dependence on the sintering condition, microstructure and composition. Excellent microwave dielectric properties (εr~17.2, Q×f~142,331GHz, τf~−23.2ppm/°C) were obtained in the x=0.08 sample sintered at 1120°C for 4h in air. In addition, the 0.17Li2O–0.83V2O5 composition was added as a sintering aid to lower the sintering temperature. The 0.5wt% 0.17Li2O–0.83V2O5 added Li3(Mg0.92Zn0.08)2NbO6 ceramic showed fairly good microwave dielectric properties of εr~14, Q×f~83,395GHz, τf~−37.2ppm/°C when sintered at 925°C for 2h. Furthermore, there was no chemical reaction between Ag electrode and the sintering aid added sample, which further demonstrates that the Li3(Mg0.92Zn0.08)2NbO6 ceramic modified with 0.17Li2O–0.83V2O5 would be a promising candidate material for low-temperature cofired ceramic (LTCC) applications.