Born in a family of Burgundian bourgeoisie, Guérard studied in Dijon from 1807 to 1814, then moved to Paris where he was first a bank employee.
Became permanent employee of the Royal Library, he devoted himself to historical research, getting a mention from the Académie française for his Discours sur la vie et les ouvrages du président Jacques-Auguste de Thou and collaborated to the L'Art de vérifier les dates.
In 1831, he was appointed at the chair of diplomatics of the École des chartes and in 1833, was elected a member of the Académie des Inscriptions et Belles-Lettres, in the seat of his master Abel Remusat, while being assistant curator at the manuscript department of the Royal Library [fr].
After the reorganization of the École des chartes in 1846, his courses became more important and in 1848, Benjamin Guérard was appointed director of the school.
At the end of 1852, he becomes curator of the manuscript department of the Bibliothèque impériale, but not for long since he died a year and a half later.