The kinetics of the oxidation of methylene blue (MB) by H2O2 in the presence of iron oxide nanoparticles has been studied. The nanoparticles of iron oxide (Fe3O4) were synthesized and characterized physico-chemical techniques. The XRD studies showed its crystalline nature. The VSM study was carried out to determine the values of the magnetic saturation parameter ~ 40.00 emu/g. The particle were of spherical shape with particle size distribution centered at 12 ± 2 nm. The FT-IR spectra indicated the presence of peaks at 585 cm -1 and 459 cm -1 due to Fe-O bond vibrations. The peak at 3424 cm -1 was assigned to the O-H stretching vibration. The H-O-H bending appeared at 1631 cm -1 . The Fe3O4 nanoparticles enhanced the rate of degradation of MB. The oxidation rate increased with the increase in Fe3O4. At pH 3, the maximum rate of oxidation of MB was observed. The rate of reaction increased with the increase in [H2O2] in the absence of Fe3O4. But in the presence of Fe3O4, the rate constant versus [H2O2] showed peaked behaviour. The CTABr increased the rate of oxidation of MB by H2O2 in the presence of Fe3O4 nanoparticles.