The title compound Fe2Mo3O12 is prepared using a wet chemical method from aqueous solutions of ferrous nitrate and ammonium molybdate. The various process parameters were optimized to get a suitable precursor, which upon calcination at 700°C for 2 h gave a well crystalline product. The product was characterized by powder XRD to have a monoclinic unit cell of Fe2Mo3O12. Its thermal expansion property was investigated by thermomechanical analyzer and high-temperature XRD. The typical monoclinic to orthorhombic phase transition happened at about 500°C, and Fe2Mo3O12 shows great NTE (macro -13.43×10-6°C-1 and micro -21.77×10-6°C-1) property during the temperature range from 500°C to 800°C.