Hexagonal needles of BaSiF6 microcrystals have been prepared by using a hydrothermal method with Ba(NO3)(2), SiO2, and HF in the presence of NH4Cl or ethylenediamine dihydrochloride as the metal chelating agent. The metal chelating agent plays an important role in controlling the aspect ratios of the BaSiF6 microcrystals. X-ray diffraction was used to confirm that the axes of the hexagonal needles of BaSiF6 are aligned along the c axis.