Bimetallic platinum copper catalysts were prepared by deposition of copper on a parent monometallic platinum catalyst. Two techniques were employed favoring the deposition of copper either on the parent metal or on the support. The activity and selectivity of copper and platinum monometallic catalysts are compared to those of their bimetallic counterparts. Copper reduces nitrates and nitrites according to a redox process but deactivates rapidly. Monometallic platinum catalysts are inactive for nitrate reduction, while nitrates are totally and rapidly reduced on Pt-Cu bimetallic catalyst when both metals are in close contact. In the bimetallic catalyst, the role of copper is to reduce nitrate to nitrite according to a redox process. In this step, the interaction between copper and platinum is of major importance to maintain copper in the metallic state by way of hydrogen adsorbed on platinum. However, copper has a negative influence on the selectivity toward nitrogen.