Objective: The survival benefits of retroperitoneal lymphadenectomy (RLNA) for epithelial ovarian cancer (EOC) remain controversial because clinical behaviors differ among subtypes. The purpose of the present study was to clarify whether RLNA increases the survival rate of advanced high-grade serous carcinoma (HGSC). Methods: This was a retrospective cohort analysis of 3,227 patients with EOC treated between 1986 and 2017 at 14 institutions. Among them, 335 patients with stage IIB-IV HGSC who underwent optimal cytoreduction (residual tumor of <1 cm) were included. Patients were divided into the RLNA group (n=170) and non-RLNA group (n=165). All pathological slides were assessed based on a central pathological review. Oncologic outcomes were compared between the two groups in the original and weighted cohorts adjusted with the inverse probability of treatment weighting. Results: The median observation period was 49.8 (0.5–241.5) months. Overall, 219 (65%) out of 335 patients had recurrence or progression, while 146 (44%) died of the disease. In the original cohort, RLNA was a significant prognostic factor for longer progression-free survival (PFS) (hazard ratio [HR]=0.741; 95% confidence interval [CI]=0.558–0.985) and overall survival (OS) (HR=0.652; 95% CI=0.459–0.927). In the weighted cohort in which all variables were well balanced as standardized differences decreased, RLNA was also a significant prognostic factor for more favorable oncologic outcomes (PFS, adjusted HR=0.742; 95% CI=0.613–0.899) and OS, adjusted HR=0.620; 95% CI=0.488–0.787). Conclusion The present study demonstrated that RLNA for stage III-IV HGSC with no residual tumor after primary debulking surgery contributed to better oncologic outcomes.