A dedicated chamber musician, he spent two summers at Ravinia’s Steans Institute and is since 2018 a member of the Boston Symphony Chamber Players. Previously, Déjardin was a member of the European Union Youth Orchestra and the Gustav Mahler Jugendorchester. He was also a founding member of A Far Cry and the Boston Cello Quartet. He has arranged numerous pieces for cello ensembles, earning six ASCAP Plus Awards and receiving commissions from Yo-Yo Ma, the Boston Symphony Orchestra, and A Far Cry. In 2013 he launched Opus Cello, his online sheet music publishing company.

Déjardin made his solo debut with orchestra at age 14 performing Haydn’s C major concerto at the Corum in Montpellier, France. In 2007 he made his Paris recital debut at Le Petit Palais as a laureate of the program Déclic supporting emerging young soloists in France.

In 2019 Déjardin released the album MOZART New Cello Duos with cellist Kee-Hyun Kim, featuring his own transcriptions. He also appears on both Boston Cello Quartet albums Pictures and The Latin Project. His first album as principal cello of the BSO, Adès Conducts Adès, was released by Deutsche Gramophone in 2020.

He serves on the cello faculty of the New England Conservatory and is regularly invited to give masterclasses in Europe, China, and North America. His instructional book Audition Day was published by Opus Cello in 2022.