In 1934, the Generalitat confirmed its status of general institution with full legal personality by the Law of the Service of Libraries.

[7] In 1936, the first reading room of the new seat, the Sala Cervantina, was opened, but the project was halted because of the Spanish Civil War (1936–1939) and not all of the necessary adaptations were completed.

[5] In 1981, two years after the restoration of Catalan self-government, it was made the national library of Catalonia by the Llei de biblioteques ("Libraries law"), approved by the Parliament of Catalonia, conferring upon it the duties of the reception, conservation, and distribution of the Catalan legal deposit.

In 1993, the Law of the Library System of Catalonia extended the institution's depository functions and helped in its modernization, which included the remodelling of the building, its reorganization and the digitization of its procedures.

[5] During the 1990s, a major renovation project further transformed the Library, including the construction of four underground levels of storage (creating more than 40 kilometres of shelf-space) and the annex building.