The museum's collection originated from the historical collection of Władysław Tarczyński and the ethnographic collection of Aniela Chmielińska, which were created in the late 19th and early 20th centuries. An important place is occupied by archaeological artefacts, militaria, tools and craftwork, guild accessories, coffin portraits, the so-called "black jewellery", memorabilia from the national uprisings, exhibits from World War I and World War II, archives, works of art by artists connected with the Łowicz region, including Józef Chełmoński, an outstanding painter born in Boczki near Łowicz. The museum is well known for its rich collection of folk art of the Łowiczans, including rural handicrafts, costumes, textiles, regional embroidery, cut-outs and decorative arts, sculpture, ritual objects. The ethnographic collections are complemented by pieces of rural architecture from the former Duchy of Łowicz displayed in two open-air museums – residential and farm buildings, a windmill, a church with a belfry and a clergy house, dating from the second half of the 18th century to the first half of the 20th century.
The museum also houses a hall of memory dedicated to the Jews of Łowicz.