In the United States, ovarian cancer (OC) accounts for the majority of gynecologic cancer mortality (19,710 new cases and 13,270 deaths in 2023). Fewer than 40% of afflicted women will have a cure, and new research indicates that pelvic inflammatory illness and hormone therapy may raise the risk of OC. Aims and objectives To evaluate the importance of preoperative PNI in ovarian cancer. To assess retrospectively association between preoperative Prognostic Nutritional Index and prognosis in patients with ovarian cancer, and to evaluate its important on disease free survival and overall survival. Subjects and methods this study was a retrospective cohort observational study. The Medical Oncology Department at Zagazig University's Faculty of Medicine hosted the study. The preoperative peripheral blood neutrophil count (PNI) was computed as follows: 10 × serum albumin (g/dL) + 0.005 × total lymphocyte count (per mm3). Using the web application "Cutoff Finder," the ideal PNI cut off value for overall survival (OS) was determined. Result the median (range) PNI was 48.22 (29.7-62). The 47.895 cutoff value discriminated patients into the high-PNI and low-PNI groups. There was significant difference between the two studied groups. A low preoperative PNI was associated with an advanced FIGO stage, CA125, ascites, residual of disease, body mass index. and significant longer Overall survival and progression free survival in patients with high-PNI. Conclusion We demonstrated that the preoperative PNI can be used as a simple and useful marker for predicting chemotherapeutic response and survival prognosis in patients with