Nanostructured BaTiO3 particles have been synthesized by hydrothermal method using a layered titania nanosheet as Ti precursor. The influence of processing parameters on the formation of BaTiO3 was investigated in this paper. The BaTiO3 particles show different shapes including irregular, sphere-like and plate-like structures by treating the titania nanosheet in different hydrothermal conditions. The dissolution-recrystallization and in situ topotactic transformation mechanisms are suggested based on observations of the factors that influence BaTiO3 formation, such as Ba(OH)2 concentration, the solvent of ethanol, and reaction temperature.