Advanced Oxidation Processes (AOPs) are considered as promising technology for waste water treatment. Photochemistry, which is a part of AOPs plays an important role in solving the problem of removal of various organic pollutants from effluents of various industries. In the present work, the photocatalytic degradation of crystal violet has been investigated in aqueous solution using nickel containing polytungstometalate under different conditions. The progress of reaction was monitored spectrophotometrically. The effect of different parameters, which affect the rate of degradation of dye; such as effect of pH, dye concentration, amount of polytungstometalate and light intensity were studied. A tentative mechanism involving hydroxyl radicals as an active oxidizing species has also been proposed.