Vanadium-doped mesoporous silica was shown to be an effective heterogenous catalyst for the oxidation of a mustard gas analogue, 2-chloroethyl ethyl sulfide (CEES), in the presence of an aldehyde and molecular oxygen. The oxidation was shown to involve a radical mechanism, which was indicated by the appearance of an induction period when the reaction occurred in the presence of a free radical scavenger. The reaction was initially selective for the oxidation of CEES to the sulfoxide, CEESO, although oxidation of the sulfoxide to the sulfonate occurred once all the CEES had been oxidized. Chemical analysis indicated that V species did not leach from the silica support when the reaction was performed in the fulorinated solvent HFE-7100.