Background: There is limited data on the optimal time interval between the last dose of neoadjuvant chemotherapy (NACT) and interval debulking surgery (IDS) in high-grade serous ovarian carcinoma (HGSC). Methods: We retrospectively identified patients with stage IIIC/IV HGSC who received NACT followed by IDS during a 15-year period (January 2003–December 2018) in our Institution. Results: Overall, 115 patients with stage IIIC/IV HGSC were included. The median age of diagnosis was 62.7 years (IQR: 14.0). A total of 76.5% (88/115) of patients were diagnosed with IIIC HGSC and 23.5% (27/115) with IV HGSC. Median PFS was 15.7 months (95% CI: 13.0–18.5), and median OS was 44.7 months (95% CI: 38.8–50.5). Patients were categorized in groups according to the time interval from NACT to IDS: 6 weeks (group D). Patients with a time interval IDS to NACT ≥4 weeks had significantly shorter PFS (p = 0.004) and OS (p = 0.002). Median PFS was 26.6 months (95% CI: 24–29.2) for patients undergoing IDS p = 0.004). Accordingly, median OS was 66.3 months (95% CI: 39.1–93.4) vs. 39.4 months (95% CI: 31.8–47.0) in the 4 week time interval NACT to IDS groups (p = 0.002). On multivariate analysis, the short time interval (p = 0.004) and OS (p = 0.003). Conclusion: We have demonstrated that performing IDS within four weeks after NACT may be associated with better survival outcomes. Multidisciplinary coordination among ovarian cancer patients is required to avoid any unnecessary delays.