The deal is worth $12.26 million, all of it guaranteed, over the next two seasons. Included in that sum is a signing bonus of $10.7 million, a source close to the player told ESPN.com's Matt Mosley.
"I'm not trying to prove anybody wrong, I'm trying to prove this organization right for making this move," Kolb said in a news conference. "I know there are a lot of expectations. When you get an extension and you get the starting quarterback position, regardless of where you're at, there's a lot of pressure and responsibility."
Kolb spent his first three seasons with the Eagles behind McNabb, but stepped in when McNabb was injured in the season opener last year at Carolina. The 2007 second-round draft choice promptly became the first NFL quarterback to throw for 300 yards in his first two starts.
He threw for 391 yards against New Orleans and 327 yards a week later vs. Kansas City.
"We're happy to have Kevin under contract for the next two seasons," Eagles coach Andy Reid said. "When given the chance, Kevin has proven to have good command of this offense and we're looking forward to having him operate as the No. 1 quarterback for the Philadelphia Eagles."
His emergence made McNabb expendable, and the No. 2 overall pick in the 1999 draft was traded to the Washington Redskins earlier this month for a pair of draft picks.
Kolb, whose contract was set to expire at the end of this season, was glad an extension could be worked out before minicamp opens.
"I want to be here long term and I think the Eagles want me here long term," Kolb said.
There was one hitch. The Eagles and Kolb did not work out a long-term deal because of the expiring collective bargaining agreement, meaning the two sides were restricted by a rule that limited annual raises in base salary to 30 percent.
The 25-year-old Kolb said minicamp begins what he hopes is a successful starting career with the Eagles. He recently became a father for the second time, adding to a whirlwind of an offseason. He feels the time is right to take control of a young offense that features blossoming receivers DeSean Jackson and Jeremy Maclin.
"It will be a different feel but, at the same time, it feels right," Kolb said. "It feels right to be the starter, it feels comfortable being out there doing the different things, running the practices that we're running right now together."
The Eagles also have Michael Vick on the roster. Vick played a limited role in short-yardage situations in his first year back in the NFL after sitting out two seasons for his role in a dogfighting operation.
This move guarantees there will be no competition for the No. 1 spot in training camp.
"I think everybody can kind of sense that there's this united feeling between everybody," Kolb said. "We're all kind of young and even though we haven't hit the field together yet as a core group, you can just kind of sense that we have this energy that we're just going to go out there and prove a lot of people wrong."
Information from The Associated Press was used in this report.