Objectives The chemotherapy response score (CRS) has been described to assess the pathological response to chemotherapy in patients with high-grade serous tubal and ovarian carcinoma. The main aim of this study was to assess the prognostic significance of CRS in patients who underwent interval debulking surgery and attained complete cytoreduction. Materials and Methods A retrospective study was conducted on patients with Fédération Internationale de Gynécologie et d'Obstétrique (FIGO) stage IIIC and IV high-grade serous tubal and ovarian carcinomas who had undergone surgery after three to four cycles of neoadjuvant chemotherapy and attained complete cytoreduction from January 2015 to July 2018. Results A total of 125 patients were included in the study. The median age of the patients was 52 years. There were 21 patients (16.8%) with a CRS of 1, 53 patients (42.4%) with a CRS of 2, and 51 (40.8%) patients with a CRS of 3. The median follow-up period was 77 months. The CRS applied on the omental samples showed significant correlation with progression-free survival (PFS; CRS of 1 vs. 2: median PFS, 17 vs. 22 months; hazard ratio, 1.73; and CRS of 2 vs. 3: median PFS, 22 vs. 54 months; hazard ratio, 2.32) and overall survival (OS; CRS of 1 vs. 2: median OS, 19 vs. 40 months; hazard ratio, 2.13; CRS of 2 vs. 3: median OS, 40 months vs. not reached; hazard ratio, 2.19). Conclusion Our study confirms that the omental CRS is significantly associated with PFS and OS in patients who attained complete cytoreduction during interval debulking surgery.