This article is a critical edition and philological analysis of the last two chapters of the biblical book of Deutero-Isaiah (Isa 54–55), based on the Coptic manuscript sa 52 and other available manuscripts in the Sahidic dialect. The first part outlines general information about the part of codex sa 52 (M 568) that contains the analysed text. This is followed by a list and brief overview of other manuscripts featuring at least some verses from Isa 54–55. The main part of this article focuses on the presentation of the Coptic text (in the Sahidic dialect) and its translation into English. The differences identified between the Sahidic text and the Greek Septuagint, on which the Coptic translation is based, are illustrated in a tabular form. It includes, for example, additions and omissions in the Coptic translation, lexical changes and semantic differences. The last part of this article aims to clarify more challenging philological issues observed either in the Coptic text itself or in its relation to the Greek text of the LXX.