TRANSFER TRACKER STATUS: Signing
The Red Bulls academy product, 20, trialed with the team in preseason after two years spent at French club FC Valenciennes.
"Kyle impressed us with the way he came into preseason," said Red Bulls head coach Jesse Marsch in a team statement. "Our academy continues to produce quality players and it's a proud day for everyone involved whenever we add one of those players to our professional ranks."
Duncan played for Valenciennes' second team in 2015-16. Last year he was promoted to the first team, which plays in Ligue 2, but did not make any competitive appearances. He has also represented the US national team at youth level.
The Red Bulls open their 2018 MLS regular season slate on Saturday against the Portland Timbers (7 pm ET; MLS LIVE in US | MLS LIVE on DAZN in Canada).