Wainwright has been sidelined by a strained left hamstring. He has been running and shagging fly balls with the team in Milwaukee, where the Cardinals wrapped a three-game series on Wednesday.
Manager Mike Matheny said the team decided that Wainwright was ready after giving him one last checkup Wednesday morning.
The Cardinals optioned Jack Flaherty to Triple-A Memphis to make room for Wainwright. Flaherty allowed one run on six hits in five innings against Milwaukee on Tuesday.
Matheny said the rest of the rotation will be pushed back a day to make room for Wainwright.