Hart was called up from Triple-A Norfolk on Saturday, Rich Dubroff of PressBoxonline.com reports.
Hart has appeared in six games for the Orioles and has continued to log quality outings between Baltimore and Norfolk this season. He will likely be utilized in low-leverage situations while with the big-league team. Expect a corresponding move prior to Saturday's game against Atlanta as the Orioles replenish their bullpen following Friday's 15-inning outing.