Opinion tribunals are extrajudicial mechanisms established by civil society to respond to failures of judicial and investigative bodies, particularly international criminal tribunals, in addressing serious human rights violations. This review presents a critical appraisal of the significant literature on tribunals of opinion through a thematic organization of their three main objectives: legitimization, the search for truth and justice in the context of impunity for serious human rights violations, and contribution to legal reform. The findings reveal a persistent gap between claimed objectives and demonstrable outcomes. The limited quantifiable impact of opinion tribunals, however, is likely symptomatic of their perception as illegitimate by entities authorized to produce law, who consequently do not refer to them. Nonetheless, the work of opinion tribunals is a reminder that truth and justice are plural concepts, essential for acknowledging the experiences of victims of human rights violations, and for exploring alternative paths to justice, beyond (inter)national tribunals.