Moral entrepreneurs are individuals or organizations that initiate public dialogue on behavior that, in their view, should be penalized. To reach this goal they have to persuade the public authorities that penalization is necessary. This article discusses how this is done based on the social construction perspective of Kitsuse and Spector. Penalization is based on the successful construction of behavior that moral entrepreneurs disapprove of into a social problem. This construction comes about in dynamic processes in which many actors, such as entrepreneurs, citizens, and politicians, interact. The central role is for the media who sets the agenda and acts as gatekeepers for issues to enter public dialogue. Without media attention, moral entrepreneurs will not succeed in constructing social problems and in reaching the authorities and the public who are needed for their success. On the other hand, the media needs the claims of the entrepreneurs in order to attract and maintain the attention of their audiences. This symbiotic relationship is pivotal in shaping society’s penal policies.