Native from Brittany, Agnès Postec studied at the CRD - Conservatoire à Rayonnement Départemental - of Brest, and at the Ecole Normale de Musique de Paris where she got unanimously a concert degree with special honours. After she reaches the CNSMDP - Conservatoire National Supérieur de Musique et de Danse de Paris - and wins her first prize in Bruno Rigutto and Aldo Ciccolini's class. Accepted in an improvement course at the Ferenc Liszt Academy in Budapest, she studies, between 1988 and 1990, piano and chamber music in György Kurtag's, Ferenc Rados' et Kornel Zempleny's classes. Then Agnès Postec starts performing as soloist or as chamber musician in France as well as abroad.

She took part in various recordings for Pierre Verany-Arion's discs, with a public success.

Holder of the C.A (teaching diploma of Paris' CNSMD), Agnès Postec actually teaches at the CRR - Conservatoire à Rayonnement Régional - of Rennes and takes part in some board of examiners of different competitions.