Adhémar graduated from the École Nationale des Chartes and held a Doctorate ès Lettre from the Sorbonne.

He was a professor at the École du Louvre and at the Université Libre de Bruxelles.

He introduced France to the ideas and methods of Erwin Panofsky, Meyer Schapiro, and Edgar Wind by broadening its analysis and research to widen the field of human mentality history.

He published articles, books, and catalogues, and was considered one of the world's foremost experts on prints (with a predilection for the 19th century).

Adhémar was the editor of the Gazette des Beaux-Arts until his death, and was the founder, in 1963, of the Nouvelles de l'Estampe, a scholarly journal on prints.