Vieira departs after two and a half years at the helm having led the team to two consecutive playoff appearances and with a current second place standing in the Eastern Conference.
In 2015, Vieira left his role as head coach of Manchester City's Under-21s after signing a three-year contract with New York City. He was also briefly linked to the Arsenal position following Arsene Wenger's departure. He replaces Lucien Favre at OGC Nice, who finished 8th in the Ligue 1 table last season, just missing out on Europa League football.
But as a coach he has only been part of the City Football Group - which owns both the Manchester and NY clubs. "We know that leaving the club has been a hard decision for him, but we understand his choice to return to Europe where he spent his whole playing career", team vice chairman Marty Edelman said.
Vieira is set to take his three assistants with him to Nice - Christian Lattanzio, Kristian Wilson, and Matt Cook - all of whom previously worked for him with Manchester City's youth squad.
"I know we have a very talented team, I have watched numerous matches and I enjoy the way the team plays and I now can't wait to begin working with the players on the training pitch", the Catalan said in a release.
NYCFC poached Manchester City assistant coach - and Pep Guardiola's right-hand man - Domenec Torrent, who becomes the third coach in the team's short history. "I know we have a very talented team".
Edelman was pleased to move so quickly to replace Vieira.
"Domenec is someone we know really well and have great confidence in as both a person and as a coach".
The Frenchman earned 107 caps for his nation and was part of the team that won the 1998 World Cup and the European Championship two years later.