In this article, we describe theoretically-based research on a new method to reduce prejudice and discrimination. The method is based on increasing people’s perceived variability of an out-group. Our research allowed us to generate a versatile experimental paradigm for investigating cognitive processes related to prejudice. It also led to the development of an effective tool that policy makers and managers can use to reduce prejudice in the real world. We describe several randomized field and laboratory experiments in which an increase of perceived variability led to a decrease in prejudice and discrimination. We also describe the results of research in which we tested the effectiveness of a ready-to-be-used intervention in a variety of social settings.