On his Web site, Fitzgerald said he will make $33 million over the first three years of the contract.
The contract also includes a no-trade clause, which means Fitzgerald would have to approve any move to another team.
"This is what I wanted to happen," he said on a conference call during an airport layover during a trip to South America. "There was a great deal of dialogue through this whole process and everybody got what they wanted."
Over the final two years of his old deal, Fitzgerald was scheduled to make $14,592,500 in 2008 and $17,355,000 in 2009. That put the team in a tight cap bind -- with less than $400,000 of cap room remaining -- so signing players was tough until Arizona struck a deal with Fitzgerald. The Cardinals had only 48 players on their roster and only 16 players on defense.
The team was trying to find a way to convince Fitzgerald to sign a six-year deal. In the end, Fitzgerald got his way and signed a four-year deal.
"Our commitment was to make sure we continue to make progress with our football team, and we feel good about the fact that we were able to keep a player of Larry's caliber," general manager Rod Graves said. "We are going to continue to do that with all our core players."
Earlier, the team placed the franchise tag on linebacker Karlos Dansby, but Graves has said efforts will continue to sign him to a long-term deal.
Fitzgerald will receive a $15 million signing bonus Tuesday. His base salary will be $2 million, giving him a $17 million payout this year. He has a $5 million option bonus in 2009. Over the four years of his contract, he will receive $30 million in guarantees.
The new deal will save the team $8.842 million in cap room, dropping Fitzgerald's salary cap number from $16,485,000 to $7,643,334.
Fitzgerald caught 100 passes for 1,409 yards and 10 touchdowns for the Cardinals last season. In 60 career games over four seasons, all in Arizona, he has 330 receptions for 4,544 yards -- a 13.8 yards-per-catch average -- and 34 touchdowns.
"When you have a player like Larry, who produces like Larry, your focus is going to be on keeping those players," said coach Ken Whisenhunt, who in his first season directed the Cardinals to an 8-8 record, their best mark since 1998.
He and Anquan Boldin have formed one of the league's top receiving tandems. Boldin also has made the Pro Bowl twice.
"When you have two receives the caliber of Larry and Anquan, it makes it tough to defend you," Whisenhunt said.
Fitzgerald has said all along that he wanted to remain with Arizona, the team that chose him as the third pick overall out of Pittsburgh in 2004.
"Contract negotiations sometimes can go back-and-forth a lot, but I knew in my heart that the Cardinals wanted me to stay a Cardinal and I know that they knew I wanted to be a Cardinal," he said.
Fitzgerald was a lifelong friend of Dennis Green, who was fired as Cardinals coach a year ago. But he has warmed to Whisenhunt.
The two sat together courtside at Sunday's NBA game between San Antonio and Phoenix. There were many discussions between the two, Whisenhunt said.
"It was so helpful having someone I could talk to because he really talked to me and helped me understand, from a business standpoint, where the team was," Fitzgerald said. "But then he could also relate to me as a player. ... The more and more I talk to him, he is a man I want to go out and play for because he stands for something. I am happy to go out and play for a man like that."
Fitzgerald said he was anxious to get the deal done so attention would be diverted elsewhere.
"I am a guy who doesn't like to be in the spotlight," he said. "I would rather go unnoticed and do my job and help my team where I can and kind of go under the radar."
John Clayton is a senior NFL writer for ESPN.com. Information from The Associated Press was used in this report.