Dimethyl methylphosphonate (DMMP) is an important simulant of organophosphates pesticides and chemical warfare nerve agents. Here, we investigated the catalytic decontamination of DMMP on Fe-oxide impregnated mesoporous Al2O3. Fe-oxide/Al2O3 sample was prepared via the temperature regulated chemical vapor deposition of Fe-oxide on mesoporous Al2O3 and post-annealing at 750 °C. The Fe-oxide/Al2O3 and bare Al2O3 samples were exposed to DMMP-containing dry air at room temperature to study the effects of Fe-oxide impregnation on the reactive adsorption of DMMP. The facilitation of DMMP degradation into CO2 and methanol at room temperature in the presence of nano-dispersed Fe-oxide was evidenced by gas-chromatograph and Fourier transform-infrared (FT-IR) absorption spectroscopy. In addition, temperature programmed oxidation (TPO) experiments and gas chromatography (Agilent, 6890) equipped with mass spectrometer (Agilent, 5973N) (GC/MS) analyses revealed that the minimum temperature that was required for total oxidation of DMMP into CO2 can also be lowered by Fe-oxide impregnation in mesoporous Al2O3.