Modality, a semantic category related to the attitude of the speaker against the proposition, found its place with Aristotle (384-322 BC) in philosophy and logic studies, and from the nineteenth century, research on modality in linguistics literature have become widespread. The modern modality studies, which began with Jespersen (1860-1943) in linguistics, were carried out by the researchers on a semantic, morphologic and syntactic stage. Among these researchers, Palmer, has examined modality typological, and he has signed a reference book in the literature with his unique modality categorization. In this study, the epistemic modality categories of The Book of Dede Korkut, which tells the social and political life of Oghuzes and gives a rich content to researchers for the study of modality in terms of the speaker and the listener, are discussed with the criteria determined by Palmer, and based on the data obtained from the research, Palmer's classification of epistemic modality has contributed to new categories.