The article deals with the contribution of A. Dulzon to the development of Yeniseian linguistics. The first scientific works on the so-called Paleo-Siberian languages, i.e., on the Yeniseian language family – including Ket, Yug, Kott, Assan, Arin, and Pumpokol – appeared in the 18th century. These studies were conducted by natural scientists, historians, and scholars such as I. Georgi, P. Pallas, G. Müller, I. Fischer, I. Gmelin, and D. Messerschmidt. M. Castrén was the author of the first grammar of the Kott and Ket languages: “Versuch einer JenisseiOstjakischen und kottischen Sprachlehre: nebst Wörterverzeichnissen aus den genannten Sprachen”. His work, which was published in 1958, was the only systematic scientific study of these languages for a long time. It was not until after the October Revolution in 1934 that a comprehensive description of the Ket language in Russian, written by N. Karger, appeared. The publications of A. Dulzon and E. Kreinovich marked a new stage in the history of Yeniseian language studies. Andrey P. Dulzon was awarded the USSR State Prize for his monograph, ‘The Ket Language,’ and both scholars and the state highly recognized his work. The significance of A. Dulzon’s work should be viewed from three perspectives: the collection of linguistic material on the Yeniseian languages (76 volumes of field notes, the Ket-Russian dictionary in card index format), publications and scientific research, primarily on the Ket and Yug languages (more than 30 scholarly treatises and 100 texts in Ket and Yug languages), and the training of highly qualified researchers – scientists who continued their studies in the field of Yeniseian linguistics (28 dissertations on Yeniseian languages defended by Dulzon’s students and their successors). It is important to emphasize the comprehensive approach taken by A. Dulzon in his work on the study of the Yeniseian languages. He regarded Yeniseian linguistics as an integral part of the broader topic of the origins of the Siberian indigenous peoples, which is reflected in the wide range of topics covered in his publications.