Nanoscaled zerovalent iron (ZVI) encapsulated in carbon spheres (nano-Fe⁰@CS) were prepared via a hydrothermal carbonization method, using glucose and iron(III) nitrate as precursors. The properties of the nano-Fe⁰@CS were investigated by X-ray diffraction (XRD), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption/desorption isotherms. Nano-Fe⁰@CS was demonstrated, for the first time, as an effective material in activating Oxone (peroxymonosulfate, PMS) for the oxidation of organic pollutants. It was found that the efficiency of nano-Fe⁰@CS was higher than ZVI particles, iron ions, iron oxides, and a cobalt oxide. The mechanism of the high performance was discussed. The structure of the nano-Fe⁰@CS not only leads to high efficiency in the activation of PMS, but also good stability. This study extended the application of ZVI from reductive destruction of organics to oxidative degradation of organics by providing a green material for environmental remediation.