The pure phase of Li3Mg2NbO6 powders was fabricated with an average grain size of 222 nm at 800 °C derived from high energy ball-milling method. By using the nanopowders as a precursor, well-densified Li3Mg2NbO6 ceramics were obtained with a relative density of 95.9% at 950 °C, which is 300 °C lower than that required by the conventional ball-milling method. Low-fired Li3Mg2NbO6 ceramics exhibited good microwave dielectric properties of er = 18.0, Q × f = 51,870 GHz, τf = − 23.01 ppm/°C, which suggests the developed materials are suitable for low-temperature co-fired ceramic applications.