The idea of being merciful to those convicted by the International Criminal Court (ICC) is uncomfortable. International criminal law (ICL) aims to address the most serious forms of harms inflicted by people on others, holding those responsible accountable through punishment. Given this, being merciful to perpetrators — treating them with kindness, compassion and leniency, particularly in punishment — seems inappropriate. The acceptability of mercy in the domestic context suggests it is worthwhile to think harder about whether there are possible justifications for mercy for perpetrators of international crimes. This article suggests that mercy has a role in ensuring perpetrators are treated as fellow human beings and in properly accounting for their individual circumstances. While the question of what role there should be for mercy in ICL is worth asking for its own sake, it also helps clarify the ways in which ICL differs from its domestic counterpart in its processes, purposes and rationale.