The rapid preparation of high-performance microwave dielectric ceramics has always been a technical challenge in the field of electronic ceramics. In this investigation, we rapidly fabricate MgTiO3–CaTiO3 microwave ceramics with homogenous microstructure and high quality factor Q by microwave-assisted sintering, highlighting the efficiency gains and sintering time reductions. As the sintering time increases from 15 min to 45 min, the bulk density and relative density of MT-CT ceramic rapidly increase. The relative density of samples sintered for 30 min exceeds 97 %, which is difficult to achieve through conventional sintering methods. Combined with Rietveld refinement and Raman spectra, it is confirmed that the cell volume of MT-CT ceramics shrinks with the extension of sintering time, resulting in the weaken of Ti–O bond strength. More refined grain size distribution and uniform microstructure obtained by microwave-assisted sintering are likely to be pivotal factors in enhancing the microwave dielectric properties of MT-CT ceramics. MT-CT ceramics sintered at 1300 °C for only 45 min by microwave-assisted sintering exhibit excellent dielectric properties: Q×f = 87, 300 GHz, εr = 20.42, and τf = 2.11 ppm/°C, thereby demonstrating the potential of achieving rapid densification of microwave ceramics through microwave-assisted sintering.