Bi-phase dispersible Fe3O4/Ag core–shell nanoparticles were successfully synthesized via non-aqueous nanoemulsion process using the triblock copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) as the surfactant. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirm the structure and morphology of the polymer-capped Fe3O4/Ag nanoparticles. The measurements obtained using ultraviolet-visible light absorbance spectrometry (UV-vis), vibrating sample magnetometry (VSM) demonstrate that the nanoparticles exhibit a surface plasmon resonance (SPR) absorption band around 430 nm from nanostructured Ag and a unique magnetic nature at room temperature. This kind of bifunctional optical-magnetic core–shell nanoparticles could be of interest in interfacial proximity effects due to the unique spatial nanostructure configuration and have potential applications in various areas.