The article is a suggestion for a possible interpretation of an identified interference of two currents − Romantic Sarmatism and Biedermeier which marked their presence in the 19th-century Polish culture. The currents provide an example of cultural diffusion which results in redefinition of the cultural identity of Polish gentry of the second half of the 19th century. Based on literary works defined as the circle of heirs of Pamiątki Soplicy Soplica’s Memoirs by Henryk Rzewuski, the article portrays not only the evolution of the old-time szlachta (Polish gentry) tradition in the context of ongoing social and cultural changes brought by the 19th century but most of all it extracts the essence and meaning of Biedermeier as a crucial cultural impulse which modernised the tradition of szlachta (Polish gentry) and ushered it into the cultural processes taking place in the 19th-century Europe.This cultural diffusion which is apparent in the relationship between Romantic Sarmatism and Biedermeier makes it possible to outline the geographical borders of cultural phenomena as well as their time frames which are indistinct when looked into only from the perspective of commonly accepted mainstream history of the 19th-century Polish culture. Also, the article pays attention to the social changes which initiated shifts and movements within the Polish culture of the 19th century.