Bifunctional magnetic-luminescent dansylated Fe3O4@SiO2 (Fe3O4@SiO2-DNS) nanoparticles were fabricated by the nucleophilic substitution of dansyl chloride with primary amines of aminosilane-modified Fe3O4@SiO2 core-shell nanostructures. The morphology and properties of the resultant Fe3O4@SiO2-DNS nanoparticles were investigated by transmission electron microscopy, FT-IR spectra, UV-vis spectra, photoluminescence spectra, and vibrating sample magnetometry. The Fe3O4@SiO2-DNS nanocomposites exhibit superparamagnetic behavior at room temperature, and can emit strong green light under the excitation of UV light. They show very low cytotoxicity against HeLa cells and negligible hemolysis activity. The T (2) relaxivity of Fe3O4@SiO2-DNS in water was determined to be 114.6 Fe mM(-1) s(-1). Magnetic resonance (MR) imaging analysis coupled with confocal microscopy shows that Fe3O4@SiO2-DNS can be uptaken by the cancer cells effectively. All these positive attributes make Fe3O4@SiO2-DNS a promising candidate for both MR and fluorescent imaging applications.