The reaction between 12-tungstocobaltate(III) and dimethyl sufoxide is reported to proceed with a very slow rate. In continuation of our interest in the polyoxometalate catalysis of oxidations, the present work of oxidation of dimethyl sulfoxide by Oxone in presence of 12- tungstocobaltate(II) was undertaken. The catalyst used in the present study acts as an outersphere reagent and the oxidant, Oxone, is the inner-sphere reagent.