BaTiO3 powders were prepared hydrothermally using TiCl4, Ba(OH)2.8H2O and NH4OH as starting materials at 150°C for 2h. The structure of the prepared nanocystalline BT powders were a metastable cubic perovskite according to XRD and HRTEM analysis, while FT Raman spectra showed that BT powders have a tetragonal structure. Hydroxyl and carbonate groups were observed in all prepared powders that showed in FTIR spectroscopy as vibrational bands. The tetragonal phase of BT powder was identified clearly by slow scan XRD at 2θ between 44.6 to 46°. The crystallite size of BT powders have increased with the increase of annealing temperature from 19 nm at room temperature to 70 nm at 1000°C.