Set up in 1942, the Polish Library in London operates as a library, archive, research institution and a cultural center serving the needs of the Polish community in Greater London and United Kingdom. It is the second largest Polish library outside Poland next to the Biblioteque Polonaise in Paris.

During World War II, it constituted a library department of the Ministry of Religious Affairs and Education of the Polish Government-in-Exile. In 1945, it acquired the name of the Polish Library and passed under the administration of the British authorities. From 1942 to 1973, the Library was directed by Maria Danilewicz. It became part of the Polish University College in 1947. After the dissolution of the College in 1953 the Library was placed under the tutelage of the Polish Research Centre. The British government announced its plans to liquidate the Polish Library and transfer its collections to the Department of Russian Studies at the University of Birmingham in 1965. However, due to the unprecedented mobilization on the part of the Polish community in Great Britain the Library was saved. The authorities transferred its ownership to the Polish Social and Cultural Association POSK.

During the 1970s and '80s, the Polish Library POSK in London systematically expanded its collections and staff. It also participated in the distribution and shipment of books published in exile and by Western publishers to People's Poland using legal and illegal means. The origins of this initiative dated back to the 1950s when the Congress of Cultural Freedom and the Central Intelligence Agency began of the largest Cold War cultural offensives, the distribution of anti-communist books to Eastern Europe. Throughout the 1970s and '80s, the book distribution program continued under the nominal guidance of another CIA-sponsored organization, the International Literary Centre (ILC) in New York. The Polish émigrés actively participated in all stages of the operation with the Polish Library POSK in London becoming one of the major distribution centers next to Paris, Rome, Stockholm, and Cologne.

During the 1980s, Zdzisław Jagodziński, the Library's director from 1973 to 2001, also started collecting Polish underground publications printed by opposition groups in People's Poland. These and other activities of the Polish Library POSK in London before the collapse of Communism in Eastern Europe make one of the most significant centers of cultural opposition to the party state in exile. At present, the Library continues its threefold mission, service to the Polish community in Great Britain, to Poland, and to United Kingdom. It collects Polonica of different formats and origins, promotes Polish culture and history, and cooperates with Polish, British, and other émigré archives, libraries, and museums.