Nb2O5 and Ta2O5 nanoparticles were prepared at a moderate sintering temperature of 700 °C using a solution method. Nitrogen doped Nb2O5 and Ta2O 5 were obtained by ammonia gas treatment at 700 °C. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV-vis diffuse reflectance spectroscopy. All the materials were used for photocatalytic decomposition of gaseous toluene irradiated with artificial solar light and pure visible light. Most of the materials were multiple crystallites with orthorhombic and monoclinic structures. Tantalum based compounds, undoped (Ta2O5 (lab)) and nitrogen doped (Ta2O 5:N (lab)), have shown much better performance than niobium based materials. Ta2O5:N (lab) decomposed gaseous toluene with a rate similar to those of Ta2O5 (lab) and Ta 2O5:N (com) in the initial 60 min but at a higher rate at extended time under artificial sunlight. Ta2O5:N (lab) decomposed about 70% toluene with artificial sunlight and 30% with pure visible light (λ = 400 nm). The material also exhibited a very stable performance with artificial sunlight and pure visible light.