The simultaneous, catalytic removal of nitrous oxide and nitric oxide in the presence of oxygen and methane or propane was studied over Co-ZSM-5. Methane is used for the reduction of nitric oxide while the nitrous oxide is able to compete for the metal sites to undergo simultaneous decomposition. Interestingly, while NOx removal by methane does not readily occur without any oxygen, the presence of nitrous oxide actually enhances the conversion of nitric oxide in the absence of oxygen.