In 1944 the Library returns to the Ciutadella as the Library of the Art Museums of Barcelona. It is now a specialised municipal library. From this period we should point out the important work of the then, and up to 1985, director of Art Museums, Joan Ainaud de Lasarte. In those years Joan Ainaud gave a great boost to acquisitions, which went from 8,000 to 80,000 pieces.

1944 Library storeroom in the old Arsenal of the Ciutadella

The old Arsenal becomes the home of the Museum of Modern Art and the Library of the Art Museums of Barcelona. The books were organized in five sequences, depending on their format.