Updated project metadata. Optimal cytoreduction to no residual disease (R0) correlates with improved disease outcome in the management of high-grade serous ovarian cancer (HGSOC) patients. Neoadjuvant chemotherapy (NACT) followed by interval debulking surgery (IDS) offers an alternate approach to management of HGSOC patients to achieve complete resection. This study assessed proteomic alterations in matched, chemotherapy naïve and NACT-treated patients tumors obtained from HGSOC patients with suboptimal (R1) versus optimal (R0) debulking at IDS. We describe distinct proteome profiles in pre- and post-NACT HGSOC tumors correlating with residual disease status providing prognostic biomarkers for residual disease at IDS as well as candidate proteins associated with NACT resistance warranting further pre-clinical investigation.