What makes an external whistleblower effective? Whistleblowers represent an important conduit for dissensus, providing valuable information about ethical breaches and organizational wrongdoing. They often speak out about injustice from a relatively weak position of power, with the aim of changing the status quo. But many external whistleblowers fail in this attempt to make their claims heard and thus secure change. Some can experience severe retaliation and public blacklisting, while others are ignored. This article examines how whistleblowers can succeed in bringing (...) their claims to the public’s attention. We draw on analyses of political struggle by Ernesto Laclau and Chantal Mouffe. Specifically, we propose that through the raising of a demand, the whistleblowing subject can emerge as part of a chain of equivalences, in a counter-hegemonic movement that challenges the status quo. An analysis of a high-profile case of tax justice whistleblowing-that of Rudolf Elmer-illustrates our argument. Our proposed theoretical framing builds upon and contributes to literature on whistleblowing as organizational parrhesia by demonstrating how parrhesiastic demand might lead to change in public perception through the formation of alliances with other disparate interests—albeit that the process is precarious and complex. Practically, our article illuminates a persistent concern for those engaged in dissensus via whistleblowing, and whose actions are frequently ignored or silenced. We demonstrate how such actions can move towards securing public support in order to make a difference and achieve change. (shrink)