The luminescence, shape, and stability of ZnS nanoparticles in ethanol are enhanced by capping the surface with (3-mercaptopropyl)trimethoxy silane (MPS) or by treating the surface with SiO2. While MPS forms an exterior network to encapsulate the ZnS surface, SiO2 surrounds ZnS nanoparticles to smoothen the surface. Both MPS and SiO2 reform ZnS nanoparticles into more stable shapes and increase their luminescence, especially in the visible region. Thus both treatments are suggested to improve various properties of optoelectronically valuable ZnS nanoparticles.