A supported Co(II)-substituted heteropolyacid salt, Cs6H2P2W17O61Co . OH2, on silica was prepared and characterized by BET surface area measurements, thermal analysis (TGA/DTA) and infrared spectroscopy. The infrared spectroscopy and thermal analysis revealed that the supported heteropolyacid salt preserves Wells-Dawson structure and is stable upto 500 degreesC. The BET result shows that by supporting the above heteropolyacid salt on silica, surface area increases. The supported heteropolyacid was used as a heterogeneous catalyst for the oxidation of aldehydes to corresponding carboxylic acids with molecular oxygen. Silica-supported heteropolyacid is an effective catalyst for the oxidation of aldehydes to carboxylic acids.