The 27-year-old Leake (9-6), acquired from Cincinnati last week for two prospects, was scheduled to make his second start for the Giants Friday in Chicago against the Cubs. He was scratched in favor of Ryan Vogelsong after his hamstring tightened up during routine sprints Monday at Atlanta.
Leake threw before Friday's game to test his injury.
Giants manager Bruce Bochy says "we decided to go ahead and put him on the disabled list and give him the full 15 days to make sure he's fully recovered. It's not worth the risk to try to get him ready for the next start."
The Giants recalled left-hander Josh Osich from Triple-A Sacramento before Friday's game to take Leake's roster spot.
Leake lost his first start with the Giants at Texas on Sunday. He allowed two runs, both on a homer by Josh Hamilton, in 6 1/3 innings.