Hélène Mercier was born in Montreal, Canada, and began studying piano at the age of six. She quickly distinguished herself in various music competitions across Quebec and Canada, winning first prizes both as a soloist and in violin-piano duos. She is also a prizewinner at the Prague International Chamber Music Competition. Her musical education was extensive and diverse: at 15, she entered the University of Music and Performing Arts Vienna, studying under Dieter Weber; she later earned a scholarship to study with Sascha Gorodnitzki at the Juilliard School in New York; she then continued her studies in France, working with Pierre Sancan at the Conservatoire de Paris and with Germaine Mounier at the École Normale de Musique de Paris. This comprehensive training laid a solid foundation for her performing career.

As a soloist and chamber musician, Hélène is regularly invited to major music festivals across Europe and North America, performing in top venues in France, Germany, Italy, Russia, the UK, Japan, South Korea, China, and beyond. She has collaborated with many world-renowned orchestras, including performances in Paris with Zubin Mehta and the Israel Philharmonic Orchestra, with Vladimir Spivakov and the Russian National Philharmonic Orchestra and the Moscow Virtuosi Chamber Orchestra; in Canada, she has worked with the Vancouver, Toronto, and Montreal Symphony Orchestras, collaborating with conductors such as Charles Dutoit, Trevor Pinnock, and Long Yu. She also performed Beethoven’s Triple Concerto with Semyon Bychkov and the Orchestre de Paris, and has successfully worked with Seiji Ozawa and the New Japan Philharmonic, as well as Long Yu and the Shanghai Symphony Orchestra, among many others.

In chamber music, Hélène has collaborated with an impressive roster of artists, including cellist Mstislav Rostropovich, violinists Vladimir Spivakov, Gidon Kremer, Henryk Szeryng, Renaud Capuçon, and Augustin Dumay. In two-piano repertoire, she has performed with Maria Curcio, Stanislav Neuhaus, Boris Berezovsky, and Louis Lortie, demonstrating exceptional ensemble skills and musical synergy.

Hélène has a prolific recording career, having received multiple international awards. She has recorded with Edward Gardner and the BBC Philharmonic, as well as with Neeme Järvi and Sir Andrew Davis, both conducting the Bergen Philharmonic Orchestra. With pianist Louis Lortie, she has recorded seven albums for Chandos, featuring works by Ravel, Mozart, Schubert, Poulenc, Rachmaninoff, Saint-Saëns, and Vaughan Williams, to widespread critical acclaim. These recordings have been named "Album of the Quarter" and "Editor's Choice" by Gramophone, and received the highest distinction, the Rosette, from the Penguin Guide. Their Vaughan Williams Concerto for Two Pianos won a Diapason d’Or, and their 2022 release of Debussy’s works for two pianos and four hands drew renewed praise. Additionally, her album of Ernest Chausson’s works with Vladimir Spivakov, released by Capriccio, received Le Choc de l’année from Le Monde de la Musique. Her recordings of Schumann, Brahms, and André Mathieu, with Cyprien Katsaris and Alain Lefèvre, released by Warner Classics, have also earned unanimous acclaim from critics and audiences alike.