Synthesis of fine BaTiO₃ powder through mechanochemically prepared precursors has been investigated. The precursors were prepared from Ba(OH)₂·8H₂O and TiO₂ by wet planetary mill treatment using acetone as a liquid medium. Pseudo-cubic BaTiO₃ was obtained after heat treatment of the precursors at 700°C for 3h. Anatase, rutile, Ba₆Ti₁₇O₄₀ and other titanates did not form during thermal treatment. The BaTiO₃ powder were sintered to densities more than 94% of the theoretical at 1250°C for 1h. The sintered materials showed a homogeneous microstructure consisting of fine grains less than 1μm, which was close to the optimum grain size for BaTiO₃ having a high dielectric constant. The well-mixed composite precursors consisting of Ba(OH)₂·xH₂O and hydrous TiO₂ were synthesized by the following successive processes; (1) extraction of hydrated water into the liquid media, (2) mechanochemical hyration of TiO₂, and (3) alloying of dehydrated Ba(OH)₂·xH₂O and hydrated TiO₂, for example TiO₂·H₂O and TiO(OH)₂, although the reactions were not completed.