The deal is worth $18 million, with $9 million guaranteed, a league source said.
"I'm very excited," Bennett said. "My agent (C.J. Laboy) and the organization have been talking for the past couple of months, and for them to get something done in a short period of time says a lot about the organization and how much they care about us."
Bennett didn't want to wait for free agency to receive a new deal.
"It's home, man," he said. "The organization has been loyal to me when they drafted me. I just wanted to be loyal to them. They had the first shot at it, they took advantage of it, and I appreciate it."
Bennett, 24, has 18 receptions and a touchdown in six games this season. Bennett missed five games with a torso injury suffered against the New Orleans Saints.
He said he didn't have any doubt the extension would happen.
"No, I never had any doubts," he said. "The organization, I feel like, they like me and know what I'm capable of doing. They see how I can fit into the offensive scheme, and of course the chemistry me and Jay (Cutler) have, just want to continue to build on it."
A third-round pick out of Vanderbilt in 2008, Bennett has emerged as Cutler's favorite target. His best season was 2009, when he caught 54 passes for 717 yards and two scores.
Jeff Dickerson covers the Bears for ESPNChicago.com and ESPN 1000.