Synthesis of Nb₂O₅ nanoparticles by mechanochemical processing has been investigated. The reactions 2NbCl₅+5Na₂CO₃→Nb₂O₅+10NaCl+5CO₂(g) and 2NbCl₅+5MgO→Nb₂O₅+5MgCl₂ led to the formation of Nb₂O₅ aggregates of 100–1000 nm in size. Addition of NaCl in the starting mixture of 2NbCl₅+5Na₂CO₃ prevented the aggregates forming. After heat treatment of the as-milled powder at 300°C, amorphous Nb₂O₅ having a high surface area of 196 m²/g was obtained. Heat treatment at 550°C resulted in a powder consisting of 10–100 nm single crystal Nb₂O₅ particles along with a network of ultrafine amorphous particles. Annealing at higher temperature led to the formation of the Na₂Nb₂O₁₁ phase.