De Page obtained his doctorate of law at the Free University of Brussels in 1919 and was appointed a judge on the Brussels court of instance. After obtaining a teaching position at the University, he was appointed a professor in 1936.
His principal work was the thirteen-volume Traité élémentaire de droit civil belge (1950), the leading textbook on Belgian civil law. De Page belonged to the École scientifique, also called "la seconde école de l'éxégese" founded before World War I in France by Gény, Esmein, Planiol, Lyon-Caen, Duguit and Hauriou. Where the older École de l' exégese held that law was synonymous to legislation and that the practice of law was the mere application of statutes, the École scientifique was of the opinion that law was a complex entity with many sources, including socio-economic factors.
Holthöfer, Ernst (2001). "De Page, Henri". In Michael Stolleis (ed.). Juristen: ein biographisches Lexikon; von der Antike bis zum 20. Jahrhundert (in German) (2nd edition ed.). München: Beck. p. 163. ISBN 3-406-45957-9.