Fox Sports' Ken Rosenthal first reported the suspension on Monday.
McKirahan, 25, appeared in three games this season, pitching 4 1/3 innings, allowing two runs, three hits and recording one hold. He was a Rule 5 selection in the 2014 Draft by the Miami Marlins from the Chicago Cubs.
He was released by Miami in spring training and picked up by the Braves.
Because of the positive drug test, McKirahan will now be subjected to six additional unannounced urine drug tests and three additional unannounced blood collections during each subsequent year for the rest of his career. He will also lose about $222,000 of his $507,500 league minimum salary.
McKirahan is the fifth pitcher in the last month to test positive for using PEDs.
Because of the positive drug test, McKirahan will now be subjected to six additional unannounced urine drug tests and three additional unannounced blood collections during each subsequent year for the rest of his career.
"We are disappointed in the decision Andrew made," Braves president of baseball operations John Hart said. "We are disappointed for him and for the ballclub. This was a guy who was beginning to pitch meaningful innings for us. The guys have been grinding. This was not good for the club."
Minnesota Twins starter Ervin Santana, New York Mets reliever Jenrry Mejia, Braves pitcher Arodys Vizcaino, and Seattle Mariners Rule 5 pick David Rollins were each suspended for 80 games after testing positive for Stanozolol.
MLB and MLBPA agreed earlier this year to increase testing and punishments for those who fail drug tests.
A first offense for a positive drug test is 80 games, up from 50 games in previous seasons. A second offense results in a 162-game ban, and a third violation would result in a permanent suspension from the sport.
- Scooby Axson