The Cubs recalled Hollowell from Triple-A Iowa on Monday, Maddie Lee of the Chicago Sun-Times reports.
Chicago placed ace Shota Imanaga (hamstring) on the 15-day injured list in a corresponding move, but Hollowell won't be a candidate to replace him in the rotation and will instead slot into a low-leverage role in the bullpen. Hollowell made one relief appearance for Chicago earlier this season, tossing two scoreless frames April 22 against the Dodgers.