Museum of Fr. Józef Jarzębowski is located in the rear part of the basilica. The museum's collection includes, among others Polish and foreign old prints from the 16th to the 18th century, royal letters and autographs, manuscripts of Polish writers from the era of Romanticism, positivism and Young Poland. An important place in the museum collection is occupied by one of the largest collections in Poland concerning the January Uprising. Two collections of white weapons - European and Eastern ones, a collection of oil paintings of European masters of the 17th and 18th centuries, papal bulls, royal documents from Władysław Jagiełło to Stanisław August Poniatowski, memorabilia of prisoners of Soviet labor camps and Nazi camps are especially valuable.