The once-capped Argentina international signed a three-year contract with the club.
"I know that the league is growing a lot and we have a lot of great players -- I'm looking forward to playing with players like David Villa and Andrea Pirlo who are two world-class champions who have achieved a lot in their careers," Moralez said of joining his new club.
Learn more about the newest #NYCFC DP, Maxi Moralez #WelcomeMaxi pic.twitter.com/dVVcpnolvC
- New York City FC (@NYCFC) February 15, 2017
"Also, to have a quality coach like Patrick Vieira, who has been one of the best in his position, recognized worldwide, is something that will help me immensely. With the experiences he's had in his career, it will be very important to help make this club great."
Later on Wednesday, NYCFC signed another winger in former Portland Timber Rodney Wallace on a free transfer from Sport Recife. NYCFC traded $75,000 in general allocation money and $50,000 in targeted allocation money to Portland for Wallace's MLS rights.
Moralez, 29, has played with clubs in Argentina, Russia and Italy in addition to his spell in Mexico with Leon.
NYCFC manager Vieira highlighted his new signing's maturity, saying: "We are really delighted to sign Maxi because he has a lot of experience at the highest level -- he's played in Italy with lots of games in Serie A and also most recently in Mexico -- he's a player who has a lot of talent and he's going to be a really good addition to the team.
"He's demonstrated his desire to come to the football club and to do well, so I'm really happy that he's decided to join us.
"Maxi is dynamic, he's direct and he's very good in one-v-one situations. He can create chances and can score goals. He's a really creative player who can make an assist -- he can create something from nothing and I believe that our fans will love him."
Moralez scored two goals and provided three assists in 14 matches for Leon in all competitions in 2016-17. Able to play on the wing, as a striker or as an attacking midfielder, he brings a versatility that excites club sporting director Claudio Reyna.
"Maxi's a creative player who will add what we needed in the final third of the field with his ability to create goalscoring opportunities for his teammates," Reyna said. "He's extremely motivated and determined to do well and is excited for the challenge of playing for New York City FC.
"He is a versatile player who will be used behind the striker but can also play in wide areas in Patrick's system.
"Maxi is an experienced player in the prime of his career and will be a positive influence for our younger players."
Moralez, Silva to make immediate MLS impact?
Herculez Gomez and Sebastian Salazar examine the impact NYCFC's Maxi Moralez and RSL's Luis Silva can have for their new clubs this season.