Montreal did not reveal the length of the contract, simply confirming that Piatti will remain at Stade Saputo beyond the original expiration of his terms in June 2018.
"We are very excited that Nacho has decided to stay in Montreal," Impact president Joey Saputo said in a news release. "He is a world-class player who belongs among the league's elite. Our supporters will have the opportunity to continue to enjoy his great qualities, which will help us reach our objectives."
“I wanted to stay in Montreal, with a club, a city and fans that I appreciate immensely.” - Nacho Piatti#IMFC— Impact de Montréal (@impactmontreal) September 28, 2017
Piatti has recorded 52 goals and 24 assists in 98 MLS matches since signing with the Impact from San Lorenzo as a designated player in July 2014.
The 32-year-old has 17 goals and six assists this season, matching the numbers he put up last year while earning Best XI honors and finishing fifth in MVP voting.
"My family and I are very happy with this agreement," Piatti said. "I wanted to stay in Montreal, with a club, a city and fans that I appreciate immensely."