The decomposition of thiourea dioxide in aqueous solution at elevated temperatures, in the presence of zinc acetate, has been used to precipitate ZnS. The important reaction pathway for the formation of sulfide ions has been elucidated, and some common ZnS phosphors have been prepared from the precipitate. The preparation of ZnS by this method is extremely simple and does not yield large amounts of liquid or gas containing volatile sulfur species. Thus, this method has been shown to be an excellent method for the preparation of ZnS phosphors, particularly copper-activated materials, requiring no purification of the reagents, with Hale production of sulfur-containing waste species, and resulting in small particle size powders without postproduction milling or separation of the powders. These phosphors have been shown to have exceptional luminescent properties compared to standard commercial materials.