UNESCO's Universal Declaration on Cultural Diversity sees cultural diversity as a source of creativity and progress. International criminal law can protect cultural diversity. However, the relationship between cultural diversity and international criminal law seems based on a paradox: everyone must respect cultural diversity, but no one may invoke it to violate international criminal law. On occasions, this paradox has been exposed to daylight in the practice of international criminal courts. For example, the Special Court for Sierra Leone held with regard to the practice of enlistment of child soldiers that it could not accept any cultural considerations as excuses for criminal conduct. Here we should note (i) that the prohibition of crimes under international law (genocide, crimes against humanity, war crimes, aggression) is generally accepted as belonging to the realm of jus cogens norms, i.e. norms from which no derogation is permitted, and (ii) UNESCO's Declaration aims at universality and not at uniformity.As international criminal law is intended to apply universally, it is vital that it takes cultural considerations on board. In this article the author reviews the literature available in the field, identifies some of the areas of international criminal law and procedure where problems with cultural diversity have been most conspicuous, and concludes that further research on the relationship between cultural diversity and international criminal law is needed.