Eagles owner Jeffrey Lurie announced the extension Wednesday and the team scheduled a news conference for 11:30 a.m. EST. Terms of the deal were not disclosed.
Reid is the winningest coach in team history, leading the Eagles to the playoffs five times and one Super Bowl in 10 seasons.
Since joining the team in 1999, Reid has won 115 games and compiled a .611 winning percentage, both best in Eagles history.
Reid took over a team that was 3-13 a season earlier and drafted quarterback Donovan McNabb in the first round of the 1999 draft. The Eagles improved to 5-11 in their first season under Reid then went 11-5 a year later and made the playoffs.
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Despite his success, Reid has drawn criticism from fans for the team's failure to win a Super Bowl. The closest the Eagles got was a 24-21 loss to the New England Patriots following the 2004 season.
The Eagles have reached the NFC championship game four other times, including three straight losses before their Super Bowl appearance. The Eagles also reached the NFC title game last season, losing to 32-25 to the Arizona Cardinals.
Reid took a leave of absence during the offseason in 2007 after two of his sons were arrested on drug charges.
One son is out of prison after completing a drug treatment program and the other is serving a two-year sentence after pleading guilty to smuggling prescription pills into a county jail.