Austin was signed as a rookie free agent by the Dallas Cowboys in 2006, and played the 2014 season with the Cleveland Browns.
The Eagles note that Austin had 348 catches for 5,049 yards and 36 touchdowns in 118 career games (69 starts). In Cleveland, Austin totaled 47 catches for 568 yards and two touchdowns in 12 games.
Austin was just the 15th undrafted player in league history to eclipse 1,000 receiving yards and the 12th with 10-or-more touchdowns in a season, the Eagles said.
Austin attended Garfield High School in New Jersey and played collegiately for Monmouth University.