The Mets recalled Hartlieb from Triple-A Syracuse on Tuesday, Tim Healey of Newsday reports.
The righty has appeared in four big-league games this season, posting a 7.71 ERA and 4:5 K:BB in 4.2 innings of work with the Pirates. Hartlieb will serve as much-needed bullpen depth following Monday's 11-inning affair that saw the Mets use six arms out of the bullpen. Jose Peraza (finger) was placed on the IL in a corresponding move.