The deal is worth $52 million and also includes $1 million per year in incentives and $27 million in guarantees, a source told ESPN's Adam Schefter.
"First of all I just want to thank [owner] Jeffrey Lurie and the entire Eagles organization," Jeffrey said in a statement. "Like I said the other day, I love it here. I'm blessed to have the opportunity to play for this organization and for these fans. Everyone has welcomed me with open arms and now I'm looking forward to being here for a long time. We have a great group here and I'm excited to be a part of it."
Jeffery, 27, has 43 catches for 619 yards and 7 touchdowns through 11 games this season. Five of those touchdowns have come during the past four games.
He was signed to a one-year deal by the Eagles in free agency this offseason. His chemistry with quarterback Carson Wentz has improved as the season has gone on.
"Alshon has been a tremendous addition to this organization on and off the field," the Eagles said in a statement. "We place a priority on making sure we are able to build the team around quality players like Alshon who embrace this team and this city the way he has. We are excited about his future here."
The former Chicago Bear expressed a desire to remain in Philadelphia when speaking to reporters last week.
"Winning championships, that's most important to me," Jeffery said. "A lot of players make a lot of money, but some of them never make the playoffs, never get to experience a lot of things. Like being here in Philly, the atmosphere where we all want that for each other. We all want to go to the playoffs. We all want to win a championship. We're all together."