Ex-Raiders quarterback Carr signs four-year deal with Saints
Carr, who turns 32 later this month, was released by the Raiders in February after nine seasons when the veteran declined to waive a no-trade clause in his contract.
"We are excited to welcome Derek Carr to the New Orleans Saints," Saints general manager Mickey Loomis said in a statement.
"Derek's experience, leadership and skill set will be an asset to our offense."
The Saints confirmed Carr's deal spanned four seasons but did not go into the details of his financial terms.
Multiple US media reports, including the NFL's official website, said Carr's contract was worth $150 million with $100 million (£83 million) in guarantees.
Carr had been linked to several teams around the NFL since his departure from the Raiders, with Indianapolis, Carolina and the New York Jets all believed to be interested in recruiting him.
His move to New Orleans will see him reunited with Saints head coach Dennis Allen, who handed the quarterback his first start in the NFL in 2014.
"I had the opportunity to work with Derek at the start of his professional football career," Allen said on Monday.
"Derek is an outstanding addition to the New Orleans Saints and I can't wait to get working with him and the rest of our team this offseason."
Carr is a four-time Pro Bowler who was chosen with the 36th pick in the NFL Draft in 2014.