After graduating from the École des chartes, he was appointed to the Département des objets d'art du musée du Louvre [fr], then at the École française de Rome.
As curator, he organized several exhibitions including (with Daniel Alcouffe [fr] and Colombe Samoyault-Verlet) Dix siècles de joaillerie française (Louvre, 1962), (with Michel Laclotte and Sylvie Béguin) L'École de Fontainebleau (Grand Palais, 1972–1973).
In 1980, he succeeded André Chastel at the Renaissance Art History chair at the École pratique des hautes études.
Meanwhile, he was a professor at the Ecole du Louvre and at the École des chartes until 2003.
Jestaz was awarded the Prize XVIIe in 2009 for his biography of Jules Hardouin-Mansart.