The article describes the emergence of a handwritten monument – Kostiantynivska Kormcha as a part the framework activity of Kostiantyniv educational center in the second half of the XVI century. The essence and origin of the term “kormcha” is clarified, its language, structural and functional features are characterized. The attention is focused on the modern facsimile edition of the ancient manuscript. Manuscript Kostiantynivska Kormcha of 1599, created in the city of Kostiantyniv (now Starokostiantyniv, Khmelnytskyi region), in the castle church school of Vasyl-Kostiantyn Ostrozky. In 2021, thanks to the enthusiasm of Ukrainian and Polish researchers, the book was digitized and published in the form of a facsimile edition. These books were of great importance not only for church life, but also for secular life. Back in the days of Kyiv state and the Galicia-Volyn principality, they regulated the legal relations of representatives of the clergy, monks and laity. Some legal concepts, principles and norms have been consolidated in the legal system of Ukraine to this day. So, in the analyzed collection of religious rules and social norms, we recorded Ukrainian vernacular features in the field of phonetics and morphology, woven into the Church Slavonic linguistic basis of the manuscript. In its lexical composition, the monument reflects the beliefs, traditions, daily life of the Ukrainian community, laws and rules both for the residents of the church school and for various representatives of society in the late Middle Ages. The return of Kostiantynivska Kormcha to scientific circulation gives us a unique opportunity to join those treasures of our culture, education, and art that our state lived by in the past. In the future, the book will be interesting for linguists, historians, theologians, and local historians.