Wainwright, 29, left spring training Wednesday for additional examinations of his right elbow. Cardinals team officials said Thursday that surgery would be required.
"Tommy John" surgery, another name for ulnar collateral ligament reconstruction, requires a tendon being transplanted to replace the damaged ligament. Rehabilitation is lengthy but many pitchers have returned from the procedure to have successful careers.
Chris Carpenter, Jaime Garcia and Jake Westbrook, all currently on the St. Louis pitching staff, have undergone the operation.
"It's not a real surprise to us this morning," said Cardinals General Manager John Mozeliak of Wainwright's diagnosis, "but certainly a disappointment and a finality to this process."
Wainwright, 28, has pitched six seasons for St. Louis, building a 66-35 record and 2.97 earned run average. He became a starter in 2007 and is 64-34 since then. Last year, Wainwright was 20-11 with a 2.42 ERA and finished second in voting for the National League Cy Young Award.