Donaldson, the 2015 American League MVP, joined Cleveland just before the Aug. 31 waiver deadline. Because of an assortment of injuries, he was limited to just 16 games with the Indians and had only one hit in the postseason.
The 32-year-old Donaldson batted a combined .246 with eight home runs and 23 RBIs in 52 games for Cleveland and Toronto last season. He missed more than three months in the middle of the season with a lingering calf injury, which also hampered him during spring training.
But when healthy, Donaldson has been one of the league's most dangerous hitters.
He batted .270 with 33 home runs and 78 RBIs despite playing just 113 games during an injury-shortened 2017 season. He was a centerpiece of Toronto's powerhouse offense that made the playoffs in 2015 and 2016, and he led the league with 41 home runs and 123 RBIs while winning the MVP in 2015.
The three-time All-Star selection followed that with 37 homers and 99 RBIs in 2016.
The short-term deal with the Braves gives Donaldson a chance to show he's healthy and back to form, potentially setting up a huge payday in the next free-agent market.
For Atlanta, it provides another much-needed slugger in the middle of the order to go with Freddie Freeman, especially since it's not known if the team will make a serious run at bringing back free-agent outfielder Nick Markakis.
Donaldson and Braves general manager Alex Anthopoulos have a relationship that goes back to their days in Toronto. Anthopoulos served in the same post for the Blue Jays until 2015, working out the blockbuster trade that acquired Donaldson from the Oakland Athletics.
Atlanta's signing of Donaldson raises questions about the future of 24-year-old Johan Camargo, who had a breakout season at third base. He hit .272 with 19 homers and 76 RBIs before going 0-for-15 in a National League Division Series loss to the Los Angeles Dodgers.
Camargo, who has also played shortstop, second base and even one game in left field during his brief big league career, could upgrade Atlanta bench as a super-sub -- a big priority after the Braves went with a playoff roster that included journeymen Ryan Flaherty and Lane Adams.
The Braves designated left-handed pitcher Adam McCreery for assignment to make room on the 40-man roster for Donaldson.
The Associated Press contributed to this report.