A method for the simultaneous removal of nitrogen oxides and laughing gas from a stream containing nitrogen oxides and laughing gas, wherein a first catalyst that contains cobalt and, as support, an inorganic metal oxide, and a second catalyst that contains iron and, as support, an inorganic metal oxide, are used. In particular the method is carried out in such a way that (a) the gas stream containing nitrogen oxides and laughing gas is reacted with a reducing gas, the reducing gas comprising a saturated hydrocarbon, in the presence of the first catalyst and (b) the gaseous product from step (a) is reacted with a reducing gas, the reducing gas comprising a saturated hydrocarbon, in presence of a second catalyst. The catalyst system can be used for the treatment of off-gases from a nitric acid plant.