The 37-year old Italian called time on his extensive playing career in October before being linked with the head coaching role at the Saputo Stadium which eventually went to Frank Klopas.
However, the World Cup winner is now back with the Impact as a consultant to the technical staff who will assist Klopas and coaching team for the 2014 MLS season.
"Alessandro knows the players well, the coaching staff and the philosophy of our club," said sporting director Nick De Santis in a statement.
"He'll help the coaching staff throughout the entire season, principally as a video analyst, providing reports on our games and those of our opponents.
"We hope that this experience will be beneficial for him, knowing that he wants to become a head coach one day."
Nesta first joined the Impact in July 2012 after a distinguished career in his homeland of Italy with Roman side Lazio and Milan giants AC.
Nesta, who is rated as one of the best central defenders ever, made 31 MLS appearances for Montreal before ending his playing days at the end of the 2013 season.
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