The sintering process and phase transformation of submicrometer powder compacts of TiO2 were investigated using 2.45 GHz microwave radiation. The microwave-sintered samples were densified more rapidly and at much shorter time and lower temperature than that of the conventionally sintered samples. Also, an accelerated phase transformation from anatase to rutile was observed in microwave processing when the dwell time is cut down from 6 h in conventional to 30 min in microwave at 1000 °C. The samples sintered in microwave show a refined microstructure and smaller grain sizes at high density near 98–99% theoretical. In addition, the reasons for rapidly heating behavior and enhanced sintering on TiO2 in microwave are discussed.