Purpose: Median overall survival (OS) after diagnosis of glioblastoma (GBM) remains 15 months amongst patients receiving aggressive surgical resection, chemotherapy and irradiation. Treatment of patients with a poor preoperative Karnofsky Performance Status Scale (KPSS) is still controversial. Therefore, we retrospectively assessed the outcome after surgical treatment in patients with a KPSS of ≤ 60%.Methods: We retrospectively included patients with a de-novo glioblastoma WHO °IV and preoperative KPSS ≤ 60%, who underwent surgery at two neurosurgical centres between September 2006 and March 2016. We recorded pre- and postoperative tumour volume, pre- and postoperative KPSS, OS, age and MGMT promoter status.Results: 123 patients (58 females/65 males, mean age 67.4 ± 13.4 years) met the inclusion criteria. 75 of the 123 patients (61%) underwent surgical resection. 48/123 patients (39%) received a biopsy. The median preoperative and postoperative tumour volume of all patients was 33.0 ± 31.3 cm3 (IR 15.0–56.5cm3) and 3.1 ± 23.8 cm3 (IR 0.2–15.0 cm3), respectively. The median KPSS was 60% (range 20–60%) preoperatively and 50% (range 0–80%) postoperatively. The median OS was 123 ± 220 days (IR 52–395 days). Age (p<0.001, HR: 1.045 [95% CI 1.022–1.068]), postoperative tumour volume (p=0.02, HR: 1.016 [95% CI 1.002–1.029]) and MGMT promotor status (p=0.016, HR: 0.473 [95% CI 0.257–0.871]) were statistically significant in multivariate analysis.Conclusion: Patients with a preoperative KPSS of ≤ 60% benefit from low postoperative residual tumour volumes. Age and MGMT-methylation status were also significant prognostic parameters in this patient cohort.