The Study focuses on the characterization of platinum-doped titanium dioxide-coated magnetic poly(methyl methacrylate) (Pt-TiO2/mPMMA) microspheres as a novel photocatalyst. The Pt-TiO2/mPMMA microspheres were prepared by a modified suspension polymerization process, followed by titania-coating and Pt-doping. The Pt-TiO2/mPMMA microspheres were synthesized with various Pt-doping levels in the range of 0.6-1.5 wt % TiO2 for comparison. The morphology, composition, Pt-doping content, and magnetic properties of the Pt-TiO2/mPMMA microspheres were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and superconducting quantum interference device. As a result, the superparamagnetic Pt-TiO2/mPMMA microspheres were successfully synthesized with particle sizes of 5-11 mu m. The magnetite and TiO2 contents of the Pt-TiO2/mPMMA microspheres were estimated as 7.69 and 16.7 wt %, respectively, while the corresponding saturation magnetization was measured as about 4.39 emu/g. Furthermore, the doped Pt nanoparticles in the metallic state were found to have a particle density of (27.5-33.5) x 10(8) cm(-2) on the surface of the PtTiO2/mPMMA microspheres. This density was found to increase with the synthesized Pt-doping concentration. The photocatalytic activity of the Pt-TiO2/mPMMA microspheres was further examined using the photodegradation of dimethyl phthalate in an aqueous solution. Dimethyl phthalate as one of the most common phthalic acid esters has been frequently detected in wastewater effluents and river water. Furthermore, the concentration of total organic carbons was monitored as an index of mineralization. A distinct photocatalytic efficiency improvement was shown with the employment of the Pt-TiO2/mPMMA microspheres as compared to the TiO2/mPMMA microspheres or direct photolysis.