Fluorescent/magnetic nanoparticles are of interest in many applications in biotechnology and nanomedicine for its living detection. In this study, a novel method of surface modification of nanoparticles was first used to modify a fluorescent monomer on the surfaces of magnetic nanoparticles directly. This was achieved via iron(III)-mediated atom-transfer radical polymerization with activators generated by electron transfer (AGET ATRP). Fluorescent monomer 9-(4-vinylbenzyl)-9H-carbazole (VBK) was synthesized and was grafted from magnetic nanoparticles (ferroferric oxide) via AGET ATRP using FeCl(3)center dot 6 H(2)O as the catalyst, tris(3,6-dioxaheptyl)amine (TDA-1) as the ligand, and ascorbic acid (AsAc) as the reducing agent. The initiator for ATRP was modified on magnetic nanoparticles with the reported method: ligand exchange with 3-aminopropyltriethoxysilane (APTES) and then esterification with 2-bromoisobutyryl bromide. After polymerization, a well-defined nanocomposite (Fe(3)O(4)@PVBK) was yielded with a magnetic core and a fluorescent shell (PVBK). Subsequently, well-dispersed bifunctional nanoparticles (Fe(3)O(4)@PVBK-b-P(PEGMA)) in water were obtained via consecutive AGET ATRP of hydrophilic monomer poly(ethylene glycol) methyl ether methacrylate (PEGMA). The chemical composition of the magnetic nanoparticles' surface at different surface modification stages was investigated with Fourier transform infrared (FT-IR) spectra. The magnetic and fluorescent properties were validated with a vibrating sample magnetometer (VSM) and a fluorophotometer. The Fe(3)O(4)@PVBK-b-P(PEGMA) nanoparticles showed an effective imaging ability in enhancing the negative contrast in magnetic resonance imaging (MRI).