For newly diagnosed glioblastomas treated with resection in association with the standard combined chemoradiotherapy, the impact of Carmustine wafer implantation remains debated regarding postoperative infections, quality of life, and feasibility of adjuvant oncological treatments. To assess together safety, tolerance and efficacy of Carmustine wafer implantation and of extent of resection for glioblastoma patients in real-life experience. Observational retrospective monocentric study including 340 consecutive adult patients with a newly diagnosed supratentorial glioblastoma who underwent surgical resection with (n = 123) or without (n = 217) Carmustine wafer implantation as first-line oncological treatment. Carmustine wafer implantation and extent of resection did not significantly increase postoperative complications, including postoperative infections (p = 0.269, and p = 0.446, respectively). Carmustine wafer implantation and extent of resection did not significantly increase adverse events during adjuvant oncological therapies (p = 0.968, and p = 0.571, respectively). Carmustine wafer implantation did not significantly alter the early postoperative Karnofsky performance status (p = 0.402) or the Karnofsky performance status after oncological treatment (p = 0.636) but a subtotal or total surgical resection significantly improved those scores (p < 0.001, and p < 0.001, respectively). Carmustine wafer implantation, subtotal and total resection, and standard combined chemoradiotherapy were independently associated with longer event-free survival (adjusted Hazard Ratio (aHR), 0.74 [95% CI 0.55-0.99], p = 0.043; aHR, 0.70 [95% CI 0.54-0.91], p = 0.009; aHR, 0.40 [95% CI 0.29-0.55], p < 0.001, respectively) and with longer overall survival (aHR, 0.69 [95% CI 0.49-0.96], p = 0.029; aHR, 0.52 [95% CI 0.38-0.70], p < 0.001; aHR, 0.58 [95% CI 0.42-0.81], p = 0.002, respectively). Carmustine wafer implantation in combination with maximal resection, followed by standard combined chemoradiotherapy is safe, efficient, and well-tolerated in newly diagnosed supratentorial glioblastomas in adults.