The designation means the Braves have 10 days to release or trade him.
Mondesi was dropped from the roster to make room for left-hander Mike Hampton, who was taken off the 15-day disabled list to pitch Tuesday night at Washington. He had a strained left forearm.
The 34-year-old Mondesi, who signed as a free agent in January, was struggling. He batted just .211 with four homers and 17 RBI.
He had been told by the club over the weekend that he would no longer be a starter in right field and was being given a few days to ponder his future.
"He's been around a long time and deserves this kind of an opportunity to contemplate what's next for him," General Manager John Schuerholz had said. "So we're giving him that. That's the right thing to do and the fair thing to do."
Mondesi has a .273 career average with 271 homers and 860 RBI.