Of all the auxiliary sciences of history, genealogy and heraldry are probably the best represented in the Library's collections.
The early part of the collection – the historic core and the revolutionary confiscations – accounts for some 200 titles, to which should be added about 120 manuscripts. It includes the classic reference works: treatises on coats of arms, genealogies and armorial bearings for the nobility, royal officials, judicial institutions, orders of knighthood, congregations, etc., and the genealogical history of the great families. This collection swelled in the 1880s, because the ministerial decree which moved the library of the learned societies into the Mazarine's buildings brought an influx of documentation on local and regional French history. The decree attributed general works of history and local archaeology directly to the Mazarine Library. When the library of the learned societies left, in 1888, this trend continued, in particular with the attribution of legal deposit copies of books on heraldry, and was confirmed decisively with the reform of the legal deposit in 1925, which sent the Library a copy of the printer's legal deposit of all French publications on local history. This attribution enabled the Library to accompany the broadening and democratisation of genealogical research in the last quarter of the twentieth century, shown by numerous publications, monographs (1,000 since 1975, compared with a third of that number up to that date), local, departmental or regional collections or journals (at least 20 on genealogy alone) published by specialist associations or learned societies from all over France. The library adds to or updates its reference works, in particular by the regular acquisition of genealogical and heraldic tools, available in open access.
The Library's heritage collections, both manuscripts and printed books, constitute a considerable corpus of heraldic devices, painted, drawn, printed, or engraved coats of arms.