Another collection which is part of Cieszyn Library is closely related to the cultural history of Cieszyn. It is the library of the Polish Ethnological Society, an organization with scientific ambitions whose establishment in Cieszyn in 1901 was inspired by Reverend Józef Londzin (1862-1929). For many years, the Ethnological Society collected all sorts of monuments of Silesian spiritual and material culture, which then served as research material used to examine the history of the region. Józef Londzin was a bibliophile, so books held a special place in his collection. Until 1930, there were about 1,000 of them (mainly old prints). Due to the fact that the majority of the books were published or read in Silesia (e.g. 18th century old prints from Brest, Bibles handed down from generation to generation, postils, hymnals, lives of the saints, calendars etc.), the library of the Ethnological Society is one of the most interesting monuments of Silesian culture. What is particularly interesting are books with labels which indicate that they were owned by local peasant families. Their number, as well as thematic and linguistic diversity, testify for a high cultural level of the people of Cieszyn and their openness to the intellectual heritage created in different national and religious circles.

Even though in the 30s the collection of the Polish Ethnological Society was deposited in the City Museum in Cieszyn, the library kept growing. It was possible thanks to gifts which were still being sent by donators. Over time, the library established by the Polish Ethnological Society expanded several-fold and it currently includes 10,000 volumes (in that about 500 old prints). The books which stand out are numerous silesiaca and works on history, literature, geography, nature, pedagogy (including a large collection of old textbooks), as well as popular and folk publications published before 1939.

Apart from books, the Ethnological Society collected all sorts of written records and miscellanies, which now make up a separate group constituting of 9,000 bibliographic records. It is referred to as the Archives of the Polish Ethnological Society. It includes documents and acts (originals and copies), literary and scientific works, correspondence, iconography, sheet music, ephemera etc. They document all aspects of political, social, economic and cultural life from the 16th to the 20th century. The great majority of these materials are related to Cieszyn Silesia both formally and in terms of their content.