A dental bleaching composition comprises a dental bleaching agent and a polyvinylpyrrolidone thickening agent. The bleaching composition may include water, flavoring agents, a basic substance and desensitizing agents, as desired. Polyvinylpyrrolidone avoids acid etching and chelation of teeth that were problematic in bleaches using carbomer as a thickener. A delivery system for delivering the bleaching composition comprises the aforementioned dental bleaching composition in combination with a moisture-resistant barrier layer such as a dental tray or a flexible strip of material.