Joseph Mélèze-Modrzejewski began his scientific career in Poland as a student of Rafał Taubenschlag.
After his arrival in France in 1958,he taught for thirty years the legal and social history of the Hellenistic world at the Faculty of Law of Paris and at the Sorbonne.
Then following his retirement from the University in 1999, Mélèze-Modrzejewski continued for 5 years to lead a seminar on papyrology and history of rights from ancient times at the École pratique des hautes études (IVe Section, historical and philological sciences) established in 1972.
From 1979 to 2010, Mélèze-Modrzejewski taught the history of post-Exilic Judaism at the Université libre de Bruxelles (Institute of Jewish Studies Martin Buber).
As the director of the Revue historique de droit français et étranger, he participated in the management of several international journals in the field of the history of law and institutions.