In 1850, De Montaignon graduated as an archivist and palaeographer from the École des chartes, with a thesis entitled Essai de dictionnaire des anciens peintres français pendant le Moyen Âge et la Renaissance.

He began his career as attached to the Louvre and the Bibliothèque de l'Arsenal and in 1864 became secretary of the École des Chartes, with a position of substitute teacher.

In 1868, at the death of Auguste Vallet de Viriville[1] the post of professor in full at the chair of bibliography and classification of archives and libraries.

He was particularly a specialist in the poetry of the fifteenth, to which he devoted many studies and of which he gave important scientific or popular editions (Dolopathos, the Livre du chevalier de La Tour-Landry, the very large Recueil de poésies françoises des XVe XVIe (the nine first volumes alone, the next four with James Mayer de Rothschild), etc.

Following his death in 1895, Montaiglon's friends erected a memorial at his grave at Père Lachaise Cemetery,[2] which features a funerary mask by sculptor François-Léon Sicard.