The deal comes a week after the Eagles lost Michael Vick to the Jets.
Sanchez will sign a $2.25 million deal that includes a $750,000 signing bonus, a league source told ESPN NFL Insider Adam Schefter. The contract also includes up to an additional $1.75 million in bonuses, bringing the maximum value of the deal to $4 million. Sanchez can achieve his bonuses by playing up to 90 percent of the Eagles' offensive plays.
Sanchez, released last Friday as soon as Vick's deal with the Jets was complete, arrived in Philadelphia on Wednesday night and underwent a medical exam Thursday morning.
The parameters of the contract were set Monday, but the medical check was the key because Sanchez is recovering from surgery on his throwing shoulder -- a torn labrum that caused him to miss the entire 2013 season.
Sanchez, who resumed throwing recently, is said to be about 80 percent. His hope is to be ready for OTA practices later in the spring. He also had arthroscopic knee surgery last season.
Nick Foles is the Eagles' starter, but Sanchez's presence should add some intrigue. The 27-year-old Sanchez is 33-29 as a starter, plus four playoff victories. He was the presumed opening-day starter last season after outplaying Geno Smith in the preseason, but he injured his shoulder in the fourth quarter of the third preseason game.
Sanchez joins another former USC quarterback, Matt Barkley, on the Eagles' depth chart. Presumably, Sanchez will be the No. 2.
"It's a position of need for us," Eagles coach Chip Kelly said Wednesday at the league meetings in Orlando, Fla. "We played three quarterbacks last year. I don't think you can look at your roster and say, 'Hey, we're good at quarterback.' You always have to look at that position. It's the key position in this game. It's something we're always going to look at."
Vick was the Eagles' Week 1 starter last season, but he got hurt and yielded to Foles, who threw 27 touchdowns, only two interceptions and made the Pro Bowl. Vick, a free agent, wanted a chance to start, so he left for the Jets, who promised him the opportunity to compete against Smith.
As soon as Vick signed, the Jets cut Sanchez, who drew immediate interest from several teams. By Monday, it was clear he was headed to the Eagles.
Kelly got to see Sanchez during their days in the Pac-10. Kelly was Oregon's offensive coordinator in 2007 and '08, when Sanchez started against the Ducks. He played poorly in a 24-10 loss, but rebounded the following year with three touchdown passes in a 44-10 rout of the Ducks.
Sanchez, the fifth overall pick in 2009, reached the AFC Championship Game in his first two seasons. Since then, he has regressed, with 39 touchdowns and 36 interceptions.
"There are a lot of positive qualities to him," Kelly said.
If history repeats, Sanchez will get a chance at some point to start for the Eagles, who have started more than one quarterback in 19 of the last 23 seasons. Foles, entering his third year, never has played a full season.
Seattle Seahawks coach Pete Carroll, who coached Sanchez at USC, said he "can't imagine him not being a starter" in the league.
Information from ESPN NFL Insider Adam Schefter was used in this report.