The Mario Praz Museum was opened in 1995. It is located on the third floor of Palazzo Primoli. The House-Museum looks like an aristocratic twentieth century residence. 

It exhibits the collection of antiquities of Mario Praz (Rome 1896-1982), historian of literature, anglicist, essayist, and scholar of minor and major arts. It includes about one thousand four hundred works, among furniture, paintings, drawings, marbles, waxes, bronzes, silver, and crystals purchased on the Italian and European antiquarian market (France, Germany, and England). 

The furnishings offer an overview of the "filosofia dell’arredamento" (philosophy of furnishings) from the end of the eighteenth to the second half of the nineteenth century", from Neoclassic to Biedermeier. Many of the paintings even represent interiors of nineteenth century residences. 

The Mario Praz Museum together with the Boncompagni-Ludovisi Museum, the Manzù Collection, and the Andersen Museum, is part of the museum pole of the National Gallery of Modern Art.