After he finished his studies at the Conservatoire de Paris, Le Sage went to London to improve by Maria Curcio.

His curiosity for the unknown works led him to play more than twenty rare concertos by Dvořák, Schoenberg, Stravinsky, Britten and others.

Lesage is a guest of renowned groups such as the Orchestre philharmonique de Radio France, the Royal Scottish National Orchestra or the Dresden Philharmonic.

In 2000 and 2001, he obtained the grand prix du disque of the Académie Charles Cros, a Victoire de la musique classique, the Prix Caecilia [fr] and the Japanese "Record of the year" for his complete recordings of chamber music pieces by Poulenc.

On 17 August 2010, Éric le Sage was in Jonzac on the occasion of the festival organized by the cultural association of the Val de Seugne; he was then accompanied by clarinetist Paul Meyer and cellist François Salque.