The article draws on social movement theory to understand collective action against corruption in Hungary. While offering a perspective on anti-corruption activism, the article demonstrates its limits against a set of unfavourable factors. Our enquiry reveals that the political context in which anti-corruption activism develops, that is, Hungary under Viktor Orbán, critically affects its mobilising potential. Closed political opportunities prompt anti-corruption activists to adopt outsider strategies; moreover, they shape the contentious content and resonance of their discourses. Overall, our interviews with prominent anti-corruption activists reveal the limited outcomes of collective action in this field.