The principle of certainty of sentences is considered one of the basic principles of proceedings in the domestic and international law system. The question is: how is the appeal process in Iran's legal system and the International Criminal Court? The purpose of this article is to analyze and review the features and effects of the appeal, which was compiled with descriptive-analytical method. The results of the research show that appealing is a rights that have been considered for the convicted in the judicial procedures of Iran and many countries and its purpose is to ensure the implementation of justice in the final sentence. The present article pursues this basic principle with a comparative study in Iran and the legal structure of the International Criminal Court. The results show that except for the difference in the duration or effects of appeals, there are similarities between these two legal systems in terms of appeals procedures. However, the appeal structure in Iran's legal system, especially in criminal courts, includes significant order, stability and regularity, which is not present in the International Criminal Court. However, the process of appealing in the statute of the ICC has been accurately predicted and given legitimacy.