The testimony of witnesses has always been considered as one of the most important evidences to prove claims and accusations in various criminal systems. In this research, with an emphasis on criminal matters and with a descriptive-analytical method, a comparative study of the validity of testimony in international criminal courts and jurisprudence has been done. The findings of the research show that from the point of view of jurisprudence, testimony is informing a right that is expressed confirmly and its validity is not dependent on the persuasion of the judge. Regarding the international criminal courts, despite the weak role of testimony as a proof of accusation in the Nuremberg and Tokyo courts as the first generation courts, with the passage of time and the formation of the second generation international criminal courts such as the former Yugoslavia, Rwanda, Sierra Leone and finally with the ratification of the Rome Statute and the formation of the International Criminal Court, we see the increasing status of witness testimony as a proof of accusation in criminal proceedings, which can be seen mainly in the form of special protection measures for witnesses as important criminal actors.