The Persian language is one of the principal foundations of unity and identity for Persian speakers across various levels, and its expansion, strengthening, and preservation are of significant importance. In the field of preserving the Persian language, various solutions have been proposed by researchers, most of which are domestic (national) in nature. To date, this issue has not been adequately addressed within the framework of international mechanisms. The main question of this research is: What capacities and capabilities does international law offer for the preservation of the Persian language? This question has been addressed through the use of library sources and the application of a descriptive-analytical method. Therefore, the primary objective of this research is to analyze and investigate the capacities of international law for the preservation of the Persian language. The findings of the research demonstrate that establishing a regional organization centered on Persian-speaking states, supporting non-governmental organizations engaged in preserving, strengthening, and expanding the Persian language, including Persian as an official and working language in regional and global organizations of which Persian-speaking states are members, and incorporating Persian among the languages used in drafting international treaties and the statutes of regional organizations are key capacities of international law that can be utilized to preserve the Persian language.