We report a facile one-pot synthesis of Fe3O4-CdX (X=S, Se) core-shell nanoparticles and characterized them with XRD, TEM, squid magnetometer, and UV-visible absorption and PL spectrometers. We observed that the core Fe3O4 nanoparticles showed a superparamagnetism at room temperature, whereas the shell CdX (X=S, Se) showed blue-shifts from the bulk materials in UV-visible absorption spectra, due to quantum confinement effect. These superparamagnetic and optical properties of the Fe3O4-CdX (X=S, Se) core-shell nanoparticles can be used for both MR and optical imagings. This dual imaging capability will increase a possibility of an early observation of disease such as cancer.