Evans signed a four-year, $37.25 million contract extension Thursday which included $18.25 million in guarantees, according to a source. He is now the third highest-paid receiver in the NFL behind the Panthers' Steve Smith and the Cardinals' Larry Fitzgerald.
A former Bills first-round choice, Evans was scheduled to be a free agent at the end of the season. Now, he is signed through 2012.
"It's really hard to put into words. I'm very excited," Evans told The Associated Press. "I really wanted to stay here. We have a great group of guys and a great organization to be a part of."
Talks between the Bills and Evans' agent, Ben Dogra of CAA Sports, have been ongoing since last season. Evans hoped to get a deal done before the start of the regular season but time ran out. Over the past week, talks intensified to the point the deal came together Thursday afternoon.
"It took a lot of patience on both sides," Evans said, in regards to talks which opened last spring. "But they were men of their words. They told me they were going to get this deal done and that's what happened."
The Bills (4-0) are off to their best start in 16 years and could end an eight-year playoff drought, the longest in team history.
Evans has 14 catches, a team-leading 332 yards receiving and one touchdown this season. He ranks second among AFC receivers in yards and has six catches of 25 yards or longer, tying Green Bay's Greg Jennings for most in the NFL.
Evans is seventh on the Bills' career list with 4,059 yards receiving, and fifth with 30 career touchdowns receiving.
Senior writer John Clayton covers the NFL for ESPN.com. The Associated Press contributed to this report.