In return for Brown, the Bills will receive a conditional 2015 fourth-round pick that can become a 2016 third-round pick. The Bills and Eagles also swapped 2014 seventh-round selections as part of the deal.
Brown, 22, adds depth to the Bills' backfield after two seasons in Philadelphia. The Bills' top running backs, Fred Jackson and C.J. Spiller, are both entering the final years of their contracts. Brown has two years remaining on his rookie deal.
Brown saw reduced playing time last season under first-year Eagles coach Chip Kelly. In 16 games, including one start, he rushed 75 times for 314 yards with two touchdowns.
The Eagles acquired speedy running back Darren Sproles in a trade earlier this offseason, pushing Brown down the Eagles' depth chart. Chris Polk, who currently projects to be the top backup, had major shoulder surgery earlier this year.
The Bills had trade discussions with the Eagles last year to acquire Brown, sources told ESPN NFL Insider Adam Caplan.