The monodisperse ZnS nanospheres, with an average diameter of 100 nm, were synthesized through a solvothermal method. Strong photoluminescence emission from blue to green and orange can be observed by doping these ZnS nanospheres with various cations (Mn2+, Cu2+, Al3+). An investigation is reported on the coating of ZnS nanospheres by a thin shell of SiO2 or TiO2 using a sol−gel process. X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) were used for the characterization of the coated ZnS nanospheres. The photoluminescence properties demonstrated that not only the brightness of the coated nanospheres has been enhanced but also the thermal stability has been improved greatly.