In 1384 he married Marie de Craon a wealthy heiress and subsequently acquired the lordship of Chimay. This became the foundational domain for the Croy dynasty.

Jean served both the early Dukes of Burgundy, Philip the Bold and John the Fearless. He was appointed chamberlain, councilor and in 1388 Governor of Artois. In 1415 at the Battle of Agincourt Jean was killed fighting England's King Henry V. His son Jean II succeeded him as Sire de Croy, becoming an influential member of the Burgundian nobility.