The 26-year-old Pole, ranked world No. 14 by the Association of Tennis Professionals (ATP), defeated Japan's Yosuke Watanuki 4-6, 7-6, 7-6 in the second round of the men's singles on Wednesday.
The Polish player will now take on Australia's Christopher O'Connell for a place in the last four.
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