He is the son of Raymond Assayas, otherwise known as Jacques Rémy, a screenwriter/writer of Turkish-Jewish origin and Catherine de Karolyi, a Hungarian fashion designer.

[6][7] A former student of the Ecole Normale Superieure de Fontenay-Saint-Cloud, he worked in the early 80's for Rock & Folk where he ardently defended some post-punk bands like Joy Division in 1981, and New Order in 1983.

He was also a columnist in the first version of the magazine Les Inrockuptibles and has written for VSD, 7 à Paris, Actuel, and Le Monde de la musique.

He was the prime contractor for the "Dictionnaire du rock" (3 volumes, 2650 pages) which was published in 2000 by Éditions Robert Laffont, and was a columnist time in issuing Bernard Lenoir on France Inter.

He is a longtime friend of the singer Bono of U2, whom he first met him in 1980 while working as a music reporter for the magazine Le Monde de la musique.