Density-functional theory has been applied to investigate the electronic and magnetic properties of the pure and chromium-doped ZnS nanosheets via examining a number of important indicators including the electronic band structure and density of states. It is found that the pure nanosheet is a semiconductor with a band gap of about 2.525 eV. Moreover, the effect of doping the chromium atom is manifested in the form of reduction in the value of the band gap to 1.85 eV, which results in half-metallic properties for the ZnS nanosheet. Most importantly, it is verified that the chromium-doped nanosheet has an intermediate band, which can be utilized in fabricating more advanced solar cells with a high rate of photon absorption and state-of-the-art lasers with a high quantum performance.