Thin film of crystalline barium titanate, BaTiO3, has been prepared from Ti metal at 100–200°C by a new technique called “hydrothermal-electrochemical method” which could be categorized into a variety of the extended hydrothermal method. The reaction was carried out in an electrolytic cell containing 0.1–0.5N Ba(OH)2 aqueous solutions at temperatures of 100–200°C and under saturated vapor pressures. Titanium metal substrate or Ti-deposited glass substrate was used for the anode and a Pt plate for the cathode. Between the electrodes, a constant current density up to 100 mA/cm2 was applied galvanostatically for 10–80 min. Surface of the BaTiO3 film was lustrous and free from any visible defects. Thickness of the BaTiO3 films ranged from 70nm to 300nm. The adhesion between the film and substrate was so strong that no exfoliation was observed. Similar BaTiO3 thin films with thickness less than 70 nm were also formed even in simple hydrothermal conditions without applying any electric current.