Evans, 30, had been the subject of trade rumors for several days with receiver one of the Bills' deepest positions. The Ravens are seeking to improve their receiving corps.
A first round draft choice of the Bills in 2004, he caught 37 passes for 578 yards and four touchdowns in 13 games last season after starting all 16 games for the 2007-2009 campaigns. He had 1,292 yards receiving in 2006 and 1,017 in 2008.
Evans had two years remaining on a contract extension he signed in 2009 that averaged $8.2 million a year. He was due to make $3.27 million in base salary this season.
(Reporting by Gene Cherry in Raleigh, North Carolina; Editing by Steve Ginsburg)