The Orioles recalled Hart from Triple-A Norfolk on Thursday, Roch Kubatko of MASN Sports reports.
Hart was sent to Triple-A in mid-March as Baltimore opted to start the season with different left-handed options out of their bullpen. The 27-year-old had a 3.71 ERA and 1.40 WHIP with 29 strikeouts over 43.2 innings as a left-handed specialist in 2017, and should serve a similar role this season.