The effect of Ar plasma treatment on the catalytic performance of Pt/CeO2 has been studied. The catalyst was activated using different procedures separately or in combination: calcination, reduction under pure H-2 and cold Ar plasma treatment. The resulting materials were characterized by X-ray photoelectron spectroscopy, X-ray adsorption near edge structure and temperature-programmed reduction with H-2. The resulting materials were tested in the water-gas shift reaction (WGS). It has been found that the combination of calcination, plasma and hydrogen treatments leads to a very active catalyst for WGS. Furthermore, the catalyst structure performance relationship has been assessed. The plasma treatment generated electron-enriched Pt particles which show a very strong interaction with the ceria support. This favoured CO chemisorption and increased the reducibility of the support, which takes part in the WGS the reaction by favouring water splitting.