This article is to research of the onomasticon of the Kazakh heroic epic “Kobylandy Batyr”, translated into the Sakha (Yakut) language by A. N. Zhirkov, T. S. Kirillin, G. G. Torotoev and published in 2025 as part of the international book series “Epic Monuments of the Peoples of the World”. The author of the article analyzes and arranges the core of onomastic units of this epic from the point of view of translation transformation and etymologization. The main research methods are the comparative method, the method of lexico-semantic analysis, the descriptive method, and statistical analysis. Comparatively, 71 onomastic units were analyzed, as a result, 6 groups of proper names were identified: 38 anthroponyms, 11 toponyms (6 oronyms, 5 astyonyms), 11 hydronyms (8 limnonyms, 3 potamonyms), 7 ethnonyms, 2 hagionyms, 2 zoonyms. Per semasiology, all onomastic units introduced into epic circulation represent a national and cultural value, and in one way or another contribute to the interpretation of the cultural code of the people. Kirillin, Zhirkov and Torotoev all use different translation methods in their translations, such as equivalent substitution, transcription, descriptive translation, addition, omission, out-of-text commentary, etc. The author of this article raises the problem of adequate translation of proper names from Kazakh to Yakut. The translation of onomastic units is a complex process, since they belong to the number of realities. Relative to the onomastic units used as comparison material, transcription is the dominant translation method (Kirillin – 63.5%, Zhirkov – 80.3%, Torotoev – 71.8%); the second position is occupied by equivalent substitution (Kirillin – 5.6%, Zhirkov – 12.6%, Torotoev – 28.2%). This proves the initiative of translators to follow the law of the Sakha language's synharmonicity and actualize the lexical potential of the Sakha language, while preserving the centuries-old customary norms of alliterative versification. This article is relevant because it provides an optimal solution to the problem of difficult translation situations, where epic translators face difficulties in transferring onomastics from the original language to the translation language.