The article is devoted to the description of Polish marriage certificates gathered in Lodz’s Catholic parish registers, dating from the late 19th and early 20th century. The aim of the paper is both to present examples of the marriage certificates in their original version and to provide an analysis of the language. The author pays attention to the specific language features and shows the significance of the documents for scholarly research. The particular character of the Russian language influenced by Polish is discussed. Attention is also paid to the template construction of the documents and the content of each part of the certificates.