Painter is slated to compete with former sixth-round draft pick Tyrod Taylor for the backup job behind Joe Flacco.
The transaction allows Painter to play for Jim Caldwell, his former coach in Indianapolis, who was hired as the Ravens' quarterbacks coach this offseason.
Last season, Painter started eight games for the Colts with Peyton Manning out for the entire year after undergoing neck surgery.
However, Painter won no games as he passed for 1,541 yards, six touchdowns and nine interceptions for a 66.6 quarterback rating.
The former sixth-round draft pick from Purdue was ultimately benched and replaced by Dan Orlovsky.
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