International criminal law, for much of its history, has been a law characterized by dissents. However, international law scholarship has largely ignored the role of the dissenting opinion in shaping the discourse of international criminal law. This article critically examines the nature and function of dissents at international criminal tribunals at a particularly crucial moment in the life of these courts, when the project of establishing accountability for mass atrocity through criminal trials is increasingly under attack. The article argues that the dissenting opinion is a crucial legal device that can have a transformative potential in international criminal adjudication through its creation of a civic space for contestation that paradoxically shores up the legitimacy of the international criminal trial. To this end, it constructs a discrete category of dissenting opinions at international criminal courts: 'radical dissents'. The content and rhetorical style of a radical dissent enables actors invested in the project of international criminal justice to use it as a vital dissentient voice both within and outside the courtroom. Agents who operate within the confines of the legal trial, such as defendants, lawyers, appellate chambers and future judges, may channel its authority to challenge the idiom in which the majority judgment speaks. Likewise, the radical dissent could provide a legal language through which academics, victims, civil society and other affected communities continue to grapple with constructing and coming to terms with events that defy human understanding.