Synthesis of La3Ni2NbO9 and La3Ni2TaO9 double perovskite materials was successfully carried out. Both isostructural niobates and tantalates exhibited a monoclinic structure. Sample preparation via solid state reaction yielded a single phase of La3Ni2NbO9, while samples with impurities were obtained when using the sol-gel process. Nb and Ta substitution in La3Ni2MO9 had effects on the sintering behavior. The electrical conductivity of La3Ni2NbO9 was found to significantly increase with increasing temperature, but the electrical conductivity of La3Ni2TaO9 decreased with temperature when the temperature was lower than 300°C then slightly increased again at higher temperature.