The low-temperature alkoxide–hydroxide precipitation synthesis of nanosized crystalline barium titanate (BaTiO3) in nonaqueous media is presented. In this report, we show the influence of the reaction medium on the nature of the product by investigating the reaction of titanium (IV) isopropoxide with barium hydroxide hydrates in 2-methoxyethanol and benzyl alcohol, respectively. A perovskite phase precipitated only in benzyl alcohol, but not in 2-methoxyethanol. One molar equivalent of water, present in barium hydroxide monohydrate, was sufficient to hydrolyze the alkoxide and form nanocrystalline BaTiO3. Depending on the water concentration, the process led directly to crystalline powder of particle sizes ranging from 3 to 10 nm, and with a clear correlation between particle size and amount of water.