Lampard, 36, was released by Chelsea at the end of last season after his contract expired to end a 13-year spell with the London side. He joins the new Major League Soccer (MLS) franchise which is due to start in 2015.
“I want to carry on challenging myself. I want to be that leader on and off the pitch,” said Lampard during a press conference in New York.
“I’ve been watching games in the MLS for a long time back home. It’s a great opportunity and a great challenge for me.”
No decision has been yet made as to where Lampard might play until the club’s 2015 debut.
“We’re going to use the rest of the week to make a decision that’s best for the club in terms of getting him ready for 2015,” said Claudio Reyna, the club’s director of football.
“He’s a professional. A leader. He ticked all the boxes in terms of the qualities to help grow our team.”
Lampard will join Spanish striker David Villa at the new club. Villa has already agreed to go on loan to Melbourne City before the newest MLS franchise opens play in March.
Lampard spent 13 years at Chelsea, where he won the Premier League three times, the FA Cup four times, and the Champions League in 2012.
During that time he made 648 appearances and became the club’s all-time top scorer with 211 goals.
He has made 106 appearances for England, the last in England’s final game of the World Cup against Costa Rica.