The aim of this study was to prepare a Fe 3 O 4 /tetra-n-butylammonium decatungstate (TBADT) catalyst (M-DT) for the selective oxidation of aromatic amine compounds in the presence of hydrogen peroxide (H 2 O 2). The material M-DT, prepared from the interactions between TBADT and Fe 3 O 4 , was fully characterized by Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and, X-ray photoelectron spectroscopy (XPS). Electron transfers between H 2 O 2 and TBADT or Fe 3 O 4 or M-DT were studied by cyclic voltammetry (CV) using carbon-modified electrodes. The optimized M-DT/H 2 O 2 catalytic system can effectively oxidize sulfapyridine (SPD) to nitroso-sulfapyridine (N-SPD) in the pH range of 2.5 to 4.6 with an efficient (93%) and selective conversion (86%). The oxidation rate constant (1.20  10-2 min-1) is much higher with M-DT than with TBADT (2.09  10-4 min-1) or Fe 3 O 4 (4.81 10-4 min-1) alone using 5 mM H 2 O 2 as a co-catalyst. This M-DT catalyst can be reused 6 times with high efficiency and selectivity.