This paper explores the theory that transitional justice is an emergent transnational social movement. It brings together the literature on transitional justice with the literature on transnational collective action to suggest that there may be the requisite level of shared identity and coordinated action around transitional justice to constitute a social movement. The paper provides both a brief history of the collective action as well as an empirical analysis of the nature of the shared identity and coordinated action around transitional justice. The findings suggest that, while a new form of collective action has emerged around transitional justice, there are ongoing struggles to define the nature of the collectivity, particularly with regards to who constitutes a transitional justice actor, and what the goals and strategies of transitional justice are and should be. The study suggests that, whether or not there is the requisite level of shared identity and coordinated action to constitute a social movement, there will be ongoing contestation over what actors mobilizing around transitional justice can and should do to meet their varied goals.