The museum preserves, researches, protects, makes accessible and popularises past generations' rich material and spiritual heritage. The core of our collections is made up of valuable artistic, historical and ethnographic memorabilia that bear witness to the culture, history and aspirations of the people of Leszno and the region. In addition to contemporary acquisitions by donation and purchase, they included collections secured after World War II in the Depository of Monuments at the Western Institute of Leszno, donations from local government institutions and silverware and other movable property from a Moravian church taken by the Nazis and revindicated in 1962 from the former German Democratic Republic. Other historical collections depicting the culture of old Leszno include coffin portraits of Calvinist noblemen from St John's Church, portraits of fowler kings, i.e. members of the Leszno marksmen's society from 1715 to 1936, courtly images of representatives of the Leszczyński, Sułkowski and other aristocratic and noble families from the south-western Wielkopolska region.
Alongside these historical collections, which document the possessions of institutions, religious communities and bourgeois houses, the museum has been amassing art collections since its inception. Chief among our collections is a collection of Polish paintings on rural themes of the 19th to 20th century and portrait paintings.
The Judaica collection comprises approximately 100 objects, including religious objects, paintings and prints, and historical memorabilia related to the history of the Jewish community of Wielkopolska.