The team did not disclose whether Sweed tore or ruptured the tendon during the final day of the team's three-day minicamp on Sunday. Sweed had the operation on Monday, but the Steelers have not estimated how long he will be out.
If the tendon was ruptured, Sweed could miss a significant portion of the season.
Sweed, a second-round draft pick from Texas in 2008, has caught seven passes in two NFL seasons, making one reception last season. He was deactivated by the Steelers on Dec. 22 as he dealt with personal issues.