The 26-year-old Pole, ranked world No. 14 by the Association of Tennis Professionals (ATP), defeated Australia's Christopher O'Connell 6-4, 6-4 in the men's singles quarterfinals on Friday.
The Polish player will now take on home favourite Jan-Lennard Struff for a place in the championship match.
Hurkacz in February won his sixth career singles title by beating home favourite Benjamin Bonzi in the final of the Marseille Open indoor hard-court tournament in France.
The grass-court tournament in Stuttgart runs until Sunday.
(gs)
Source: PAP