Nanometer-sized zinc ferrite particles capped with a layer of surfactant were synthesized and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) techniques. The effect of the surfactant capping on the grain growth of the zinc ferrite nanoparticles was investigated. The surfactant capping effectively inhibited grain growth, and it was observed that the zinc ferrite nanoparticles with a capping layer could readily be dispersed in some organic media due to their surface modification.