The present article is devoted to a comprehensive analysis of lexical and semantic peculiarities of diplomatic lexicon of modern Persian language. Diplomatic vocabulary is considered as a special layer of socio-political language formed under the influence of historical, cultural, religious and political factors. It serves as a tool for expressing the official position of the state in international dialog, diplomatic negotiations, political statements and interstate correspondence. The author emphasizes the role of borrowed vocabulary, primarily Arabic and French, in the formation of diplomatic vocabulary. Arabic loanwords, which have penetrated the Persian language since Islamization, cover religious, political and administrative terms that have become an integral part of the official style. The author emphasizes the role of borrowed vocabulary, primarily Arabic and French, in the formation of diplomatic vocabulary. Arabic loanwords, which have penetrated the Persian language since Islamization, cover religious, political and administrative terms that have become an integral part of the official style. European borrowings, especially those of French origin, have been in active use since the 19th century. The article pays considerable attention to the stylistic characteristics of diplomatic speech. Persian diplomatic vocabulary is characterized by a high level of politeness, the use of stable expressions, complex verb constructions and traditional forms of address. Such elements of speech contribute to the observance of the norms of protocol and create an atmosphere of formality and respect. An important component is euphemization - the use of soft and veiled expressions instead of direct or potentially conflicting language. Euphemisms allow to smooth out confrontational accents and observe the norms of diplomatic etiquette. In addition, the role of Latin expressions which are used both in the original and in translation, giving the speech universality and compliance with international standards, is analyzed. Thus, the Persian diplomatic vocabulary is a multi-layered, formally organized system reflecting both national specifics and global trends in international communication.