Aim and background: Most ovarian cancer patients are diagnosed at a late stage, which correlates with a poorer prognosis. Systemic inflammation plays an important role in tumor initiation and progression. Therefore, systemic inflammation markers, including neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), are extensively studied. However, the applicability of PLR and NLR as malignancy predictors and the diagnostic accuracy in ovarian malignancy need to be clarified. The study aimed to investigate the diagnostic accuracy of PLR and NLR for malignant ovarian tumors. Methods: We included 161 patients who underwent surgery on an indicated ovarian tumor. Histopathologic confirmation of malignancy was used as a gold standard. Preoperative PLR and NLR values were compared to pathologic confirmation of malignancy. A threshold of NLR ≥3.0 was defined as high NLR, while PLR value ≥160 was considered high. The area under the curve (AUC) value of the receiver operator characteristic (ROC) curve was used to distinguish between benign and malignant individuals. Area under the curve above 0.7 is considered an acceptable diagnostic performance. Results: We found that both preoperative PLR and NLR had significantly greater values in ovarian cancer than in benign ovarian tumors (p < 0.001). High NLR patients showed greater possibility of malignancy (OR = 5.32; 95% CI: 2.52–11.21; p < 0.001). Patients with high PLR also showed comparable odds ratio for malignancy (OR = 4.03; 95% CI:1.95–8.31; p < 0.001). The sensitivity of NLR was 66.3% and specificity was 72.9%, while PLR sensitivity and specificity were 78.76 and 52.08%, respectively. The accuracy of NLR was 68.32% (AUC = 0.743) and PLR was 60.54% (AUC = 0.733). Conclusion: Both PLR and NLR have valuable accuracy in differentiating ovarian malignancies from benign ovarian tumors. These results may be important evidence to support the applicability of these cheap markers to indicate ovarian malignancy in low-resource settings.