Whereas monometallic palladium catalysts deposited on classical supports such as silica, alumina, or carbon are totally inactive for nitrate reduction, we have demonstrated that a reduced Pd/CeO2 catalyst is active for this reaction (33 mmol/(min g(met))). The promoting effect of the support, based on its redox properties, was clearly identified, nitrate reduction probably occurring through the interaction of oxygen atoms of nitrate with the oxygen vacancies created at the ceria surface upon the reduction treatment. Conversely, nitrite intermediates are converted through a classical catalytic reaction by hydrogen adsorbed on palladium sites.