The rise and development of markets under neoliberal consumerism represents a topical theme in marketing theory and is at the heart of emergent discussions on market system dynamics. While the nonprofit market sector represents a major part of the economy and is an important locus for alternative market discourses, prior studies tend to focus on well-represented groups of actors, such as corporations or consumers. Moving beyond the dyad of producers and consumers, the present study contributes to recent discussions on institutional work by examining and problematizing the role of nonprofit organizations (NPOs) as agents of market system dynamics. A qualitative discourse analysis of nonprofit marketing, conducted at one of Sweden’s largest NPOs, reveals the institutional work aimed at modifying the market for health and fitness according to alternative cultural values of, for instance, inclusiveness, democracy, and collectiveness. In particular, the article draws attention to ethical institutional work in markets, which enables organizations to strategically switch managerial focus between disparate institutional demands for purposes of creating and maintaining hybrid forms of legitimacy. However, ethical work also problematically entwines nonprofit with commercial values of profit maximization. The study contends that nonprofit consumerism thus works as a double-edged sword and may spur commercialization and market diffusion in society at large.