The article identifies and analyses the development it labels the “quantitative turn” in international criminal law. Addressing the cumulative effect of the large numbers of witnesses in international processes, the article considers quantity as an integral, and substantively beneficial, component of the law's response to atrocity crimes. The article develops a theorized understanding of the relationship between mass atrocity and mass testimony and provides a taxonomy of the functions that the quantity of testimonies fulfills in international trials: the evidentiary, didactic, epistemic, and restorative functions. Focusing on a recent case before the International Criminal Court in the matter of The Prosecutor v. Bemba, the article demonstrates how the different players in the international justice system—Prosecution, Defense, Victims, and the Court—employ the functions of quantity, while negotiating concerns over manageability and scale. The goal of this article is to prompt a debate and a more careful consideration of the potential benefits of a meaningful participation of witnesses and victims in post-atrocity proceedings. This is particularly important given the dominance of the efficiency paradigm in international criminal law (ICL) discourse, which directly impacts the quantitative turn. The article forges new ways for ICL institutions to maintain a plurality of voices and their commitment to victims while safeguarding the rights of the accused.