The manuscripts of the Lithuanian Tatars are comprised of religious works written in the Arabic script like Kitab, Tafsir, Hamail, Tajvid. These manuscripts preserved texts concerning such languages as Chagatai Turkic, Old Anatolian Turkish, Belarusian and Polish. Especially the type of manuscripts named Kitab is important as it bears relation to the Turkish language, because in the type of Kitab, Slavic translations are found between the lines of some Turkish texts. One of the texts found within the type of Kitab is the text of the mirajname that belongs to the period of the Old Anatolian Turkish. Since XIVth century numerous examples of mirajname have occurred in Turkish literature, however its appearance in the manuscripts of Lithuanian Tatars is a curious case. In this article the Eastern Turkic grammatical features in the mirajname text found in the Kitab of Ibn Abraham Koricki that belongs to the period of the Old Anatolian Turkish shall be analyzed and generally the reasons of the appearance of the Eastern Turkic forms of words and suffixes in the mirajname text written according to the grammatical characteristics of Western Turkic shall be discussed.