Nanoparticles of α-Bi 2 Mo 3 O 12 have been synthesized by a method that involves an amorphous complex precursor. The phase formation process, crystal structure and morphology of the synthesized samples were followed by TGA/DTA, XRD, TEM and SEM techniques. The effect of temperature of calcination on the surface area and optical properties of α-Bi 2 Mo 3 O 12 nanoparticles has been also investigated. The photocatalytical activity of α-Bi 2 Mo 3 O 12 nanoparticles was evaluated in the degradation of rhodamine B molecules in aqueous solution under visible light irradiation. The best photocatalyst was selected by evaluating the photocatalytic properties of samples with different calcination temperatures. The kinetic degradation of rhodamine B was adjusted with a first-order reaction with an apparent rate constant k′=1.36×10 −2 min −1 and t 1/2 =51min for the best material obtained. The mineralization degree of the dye to CO 2 and H 2 O was around 56% after 100h of irradiation.