The 39-year-old, at spring training with a minor league contract, caught his first game Sunday since a June 15 operation to repair the labrum in his throwing shoulder.
After Sunday's game Zaun said he was pleased with his physical progress but was concerned about his shoulder's stamina and wasn't sure when he would be ready to play.
General manager Jed Hoyer confirmed his retirement Monday.
Zaun hit .265 with two homers and 14 RBIs in 28 games with the Milwaukee Brewers last season.
He made his big league debut with the Baltimore Orioles in 1995 and played for nine teams. Zaun had a .252 career average with 88 homers and won a World Series title with the Florida Marlins in 1997.