Pt modified Fe3O4 magnetic nanoparticles (Fe3O4@Pt NPs) were synthesized by a simple method. The morphology and crystal structure of the as-prepared nanocomposite were characterized by TEM, XRD and EDS. The peroxidase-like catalytic activity of the synthesized nanoparticles was also investigated. Catalysis was found to follow Michaelis–Menten kinetics. The calculated kinetic parameters of the Fe3O4@Pt NPs show that they exhibited strong affinity with substrates and enhanced catalytic activity than that of Fe3O4 nanoparticles, suggesting a higher peroxidase-like activity.