Pure anatase titanium dioxide was synthesized by a microwave (MW)-assisted hydrolysis of diluted acidic solutions of titanium tetrachloride. MW irradiation combined with hydrothermal process has proved to be a very efficient and fast alternative to conventional hydrothermal technique, as an almost complete crystallization of anatase occurred in reaction times as short as 30 min. The addition of small amounts of sulfuric acid was necessary to obtain a pure anatase phase, as the presence of sulfate prevented the crystallization of trace amounts of brookite. Transmission electron micrographs showed nanoparticles arranged in spherical aggregates with 1% sulfuric acid, while less aggregated nanoparticles were obtained with 0.1% sulfuric acid.