Core-shell magnetic nanoparticles have received significant attention recently and are actively investigated owing to their large potential for a variety of applications. In this study, the synthesis and characterization properties of magnetite @ polyrhodanine (Fe3O4 @ PRh) core-shell nanoparticles have been investigated. To monitor the morphology, size, structure, thermal stability, and magnetic properties of nanoparticles, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetic analysis, and vibrating sample magnetometer were carried out. The results indicate that a thin film of polyrhodanine was coated on the surface of Fe3O4 nanoparticles. The coated shell of polyrhodanine can protect the Fe3O4 cores from being oxidized. Also, the results presented the crystalline, small size, and high magnetization value for the core-shell structure.