0.9(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4–0.1(Ca0.8Sr0.2)TiO3 (MZTS–CST) ceramics were prepared by a conventional solid-state route. The MZTS–CST ceramics sintered at 1325°C exhibited εr = 18.2, Q × f = 49 120 GHz (at 8.1 GHz), and τf = 15 ppm/°C. The effects of LiF–Fe2O3–V2O5 (LFV) addition on the sinterability, phase composition, microstructure, and microwave dielectric properties of MZTS–CST were investigated. Eutectic liquid phases 0.12CaF2/0.28MgF2/0.6LiF and MgV2O6 were developed, which lowered the sintering temperature of MZTS–CST ceramics from 1325°C to 950°C. X-ray powder diffraction (XRPD) and energy dispersive spectroscopy (EDS) analysis revealed that MZTS and CST coexisted in the sintered ceramics. Secondary phase Ca5Mg4(VO4)6 as well as residual liquid phase affected the microwave dielectric properties of MZTS–CST composite ceramics. Typically, the MZTS–CST–5.3LFV composite ceramics sintered at 950°C showed excellent microwave dielectric properties: εr = 16.3, Q × f = 30 790 GHz (at 8.3 GHz), and τf = −10 ppm/°C.