Fe-modified ZSM-5 zeolites (Si/Al = 25) were prepared by adopting the liquid ion-exchange method with nitrate and oxalate of iron as Fe precursors and their catalytic performance was studied in the N2O decomposition reaction. The results of FT-IR and H-2-TPR investigations indicated that (i) part of the iron ions could replace Bronsted acid protons at the straight channel wall (alpha sites), intersection of straight and sinusoidal channels (beta sites), and sinusoidal channel wall (gamma sites) within the ZSM-5 zeolite; and (ii) different Fe precursors gave rise to various distributions of alpha, beta, and gamma sites. We observed that the Fe-ZSM-5 catalyst prepared with iron oxalate as Fe precursor outperformed the ones prepared with iron nitrate as Fe precursor in the direct decomposition of N2O. Furthermore, the catalytic activity of iron ions located at the alpha sites was higher than those of iron ions located at the beta and gamma sites.