Nanocrystalline tetragonal-BaTiO3 powder was prepared using a hydrothermal method, under moderate conditions, and with a high precursor concentration. Characterization via X-ray diffractometry and differential scanning calorimetry confirmed that the average particle size and tetragonal content of the prepared powder were 70 mn and 80%, respectively. The sintered sample made from the prepared powder had a room-temperature dielectric constant of 6900, which was high for BaTiO3.