The 39-year-old Edmonds did not play last season but never retired.
General manager Doug Melvin has been looking for left-handed hitters to help fill out his predominantly right-handed roster. Milwaukee's outfielders include Ryan Braun, Corey Hart, Carlos Gomez and Jody Gerut.
"He is a veteran guy," Melvin told 1050 ESPN New York's Andrew Marchand. "We have Braun, Gomez and Corey Hart, who are all right-handed. He adds depth."
A four-time All-Star and eight-time Gold Glove winner, Edmonds hit .235 with 20 homers and 55 RBIs in 111 games for the Padres and Cubs two years ago. He was a big part of 100-win teams in St. Louis in consecutive seasons in 2004-05, and played on a World Series winner with the Cardinals in 2006.
Melvin called it a low risk move for the club.
"He took the year off and has the fire to want to come back," Melvin said. "I'm hoping that it works out very similar to how it worked out with Gabe Kapler."
The Cardinals traded Edmonds and $2 million of his 2008 salary in December 2007 for prospect David Freese, the leading contender for the vacant third base job in St. Louis.
Information from The Associated Press was used in this report.