As a strong greenhouse gas with a wide lifespan, nitrous oxide (N2O) reduction emissions are imperative. Transition metal oxides, especially cobalt oxides, possess superior N2O catalytic decomposition properties. A series of cobalt-incorporated HZSM-5 (Co/HZ) catalysts were synthesized by citric acid-complexion impregnation and were systematically investigated by N2O decomposition and characterizations. Co content and calcination temperature influenced cobalt species distribution and active site amount. Multiple cobalt species were found and cooperatively catalyzed N2O decomposition. Co2+ ions in cobalt species are regarded as active sites in N2O decomposition and the 10Co/HZ-800 catalyst showed better N2O catalytic decomposition performance, O2, and NO tolerance. The 10Co/HZ-800 catalyst was subjected to in situ diffuse reflectance infrared Fourier-transform spectroscopy (in situ DRIFTS) for surveying N2O adsorption patterns on the surface under different temperatures and atmospheres.