This article reports the effects of steam on the activity and stability of Fe/ZSM-5 for the selective catalytic reduction of NO with iso-butane. When the feed contained 10% of H2O, the de-NOx activity was maintained if the temperature was above the maximum conversion temperature. However, when the temperature was below the maximum conversion temperature, the catalytic activity decreased. The effect of high temperature steam treatment on the stability was also examined. After the steam treatment, the activity of Fe/ZSM-5 decreased due to the dealumination of ZSM-5 and the migration of Fe ion isolated in the ion exchange site to form ferromagnetic iron agglomerate. The physicochemical properties of the fresh and deactivated catalysts were monitored by ESR, 27Al MAS NMR, XPS, XRD, TPR and FT-IR spectroscopy.