The Library's collections, a total of 600,000 items, are built around two ensembles:

- An exceptional heritage collection, the core of which is Mazarin's (1602-1661) historic library, now numbering:

• 4,700 manuscriptsan early encyclopaedic collection of 200,000 rare and precious books
  
• 2,300 incunabula
• numerous special collections
• collections of artworks and furniture

- Current resources (books and periodicals), still growing in accordance with collection development specialised in the historical disciplines.