The article examines the phonetic and morphonological features of the Teleut language in the manuscripts of Siberian researchers from the first third and end of the 17th century. The Teleut language belongs to the central-eastern group of Turkic languages, according to other classifications – to the Siberian Turkic languages, the Kyrgyz-Kipchak languages as one of the southern dialects of the Altai language, in the manuscripts of researchers of Siberia in the first third and the end of the 17th century, on the example of somatisms and the animal world. The aim of the article is to analyze the graphics, orthography, and morphonology of words recorded by P.S. Pallas and designated by him as “Teleut”, in comparison with the modern Teleut language. The source of the vocabulary was P.S. Pallas’s “Comparative Dictionary of All Languages and Dialects,” published in 1790-1791. The basis for synchronous comparison was L.T. Ryumina’s “Teleut-Russian” (1995) and “Russian-Teleut” (2002) dictionaries, as well as the author’s expedition materials. The article uses the method of continuous sampling and the comparative-historical method. Analysis of the vocabulary from Pallas’s dictionaries shows that 77.5 % of the words (31 out of 40 pairs) from the semantic domians “body parts” and “wildlife” retain their identity with the vocabulary of the modern language of the Bachat Teleuts. Of these, 20 pairs are identical in sound composition at the deep morphophonological and superficial phonetic levels. Another 11 pairs have differences including variability of the initial *č-, vowel shift, diphthongization, delabialization, palatalization of final consonants and loss of labial harmony. Lexical discrepancies are also noted: the dropping of one of the parallel forms and the complete loss of words. It is possible that the “Teleut” language in Pallas’s dictionaries encompassed several idioms, in particular, those close to Siberian Tatar.