This paper offers a critical edition of the Divine Liturgy of St. John Crysostom according to manuscript D. Gr. 143 from the collection of the Ivan Dujčev Centre for Slavo-Byzantine Studies. The leitourgikon (from the Kosinitsa Monastery near Drama) was copied by Konstantinos Hazoropoulos in 1368, which makes the Chrysostom formulary a reliable source of a liturgical rite from the initial period of the establishment of Philotheos Kokkinos’ Διάταξις της Θείας λειτουργίας. The fragment contains archaic elements that were due possibly to an influence from peripheral eucharistic practices.