The A's said Anderson had surgery Thursday. Dr. James Andrews performed the operation to rebuild the ulnar collateral ligament.
Anderson was 3-6 with a 4.00 ERA in 13 starts this season. He went on the 15-day disabled list on June 7 because of elbow soreness.
The 23-year-old pitcher originally had a platelet rich plasma injection in his elbow and was going to see whether rehabilitation could help him. After an evaluation period, it was decided that Anderson needed surgery.
Anderson was 7-6 with a 2.80 ERA in 19 starts last year.