A platinum-group-metal-free catalyst comprising Fe-Ni alloy nanoparticles on a gamma-Al2O3 support was investigated for use in three-way catalytic converters, with particular attention being paid to its NO reduction activity. The catalyst showed activity for the simultaneous removal of NO, CO, and C3H6 in the stoichiometric NO-CO-C3H6-O-2 reaction. Low-oxidationstate Fe sites were found to be effective for NO reduction, while their oxidation by this reaction induced catalyst deactivation. Ni atoms adjacent to the low-oxidation-state Fe atoms were found to stabilize them by catalyzing the consumption of the O atoms in the nanoparticles for CO oxidation, which indirectly promoted further NO reduction.