Two novel mixed polyoxometalates of tungsten and molybdenum are synthesized via hydrothermal method from aqueous acidic solution of reagents. Their Elemental Analysis, Scanning Electron Microscopy (SEM), Ultra –Violet (UV) Analysis, Infra-Red (IR) Studies, Thermal Analyses (TG-DTA) followed by Molecular Weight Determination confirm the existence of Keggin type polyoxoanions with large number of peripheral water molecules in them.