As a student at the Paris Conservatory, he won four first prizes. His teacher was Yvonne Loriod, wife of composer and theory teacher Olivier Messiaen.

Aimard's studies with Loriod gave him a close association with Messiaen, resulting in Aimard becoming a leading interpreter of Messiaen's piano music. After graduation from the Paris Conservatory, Aimard went on to London for further studies with Maria Curcia. At Curcia's suggestion, Aimard went to Budapest, Hungary, to pursue composition studies with György Kurtág, one of that country's leading "advanced" composers.

In 1973, Aimard won first prize at the Olivier Messiaen International Competition, and shortly thereafter began his international concert career.

In 1976, Pierre Boulez, at this point an internationally famous conductor who had left the podium of the New York Philharmonic to take over the new IRCAM organization in Paris, suggested the founding of an ensemble to be permanently attached to it. Upon receiving government approval, he established Ensemble InterContemporain, one of the leading avant-garde ensembles in the world, inviting Aimard to become its regular pianist. Aimard accepted, remaining in that position for 18 years.

During the ensemble's appearances in America in 1986, he performed as soloist in Boulez's composition Rèpons in New York, Los Angeles, San Francisco, Boston, and Chicago. In 1988 at the B.A.M. concerts in New York he performed Messiaen's Oiseaux exotiques and Philippe Manoury's La Partition du ciel et de l'enfer in Carnegie Hall. He has also appeared as a piano soloist in concerto performances of traditional repertory. In that capacity he has performed with many of the world's great orchestras, including the Cleveland Orchestra, Chicago Symphony, Boston Symphony, San Francisco Symphony, Toronto Symphony, London Philharmonic, Berlin Philharmonic, Concertgebouw Amsterdam, Orchestre de Paris, and the St. Petersburg Philharmonic. His appearances in international music festivals tend to center on unusual repertory; he has played at Tanglewood, Salzburg, the Berlin Festival, the Edinburgh Festival, the Autumn Festival of Paris, and the Cologne Triennial Festival.

Upon leaving the Ensemble InterContemporain, he announced a concert series in Paris and Lyon called "Piano in the 20th Century." He followed the success of this venture with several other such concert series, including one devoted to duet performances, another tracing the influence of Johann Sebastian Bach over the centuries, and an innovative exploration of music in time and space that combined ancient music, ethnic music forms, classical music, and film music. Conductors in that series included Kent Nagano, Christoph von Dohnányi, Pierre Boulez, and Peter Eötvös.

For Sony he has undertaken a series of recordings of the complete piano music of Hungarian composer György Ligeti. In addition, he has produced television films popularizing and explaining music of his time.

Aimard has served as the artistic director of the Aldeburgh Festival (beginning in 2009) and continued appearing with ensembles around the world, including the Royal Concertgebouw Orchestra and orchestras in Chicago and Cleveland.