Background: The role of inflammation in the prognosis of cerebral venous sinus throm-bosis (CVST) has been demonstrated in a small number of studies. The platelet-to-lymphocyte ra-tio (PLR), neutrophil-to-lymphocyte ratio (NLR), and the systemic immune-inflammatory index (SII) have been studied as prognostic inflammatory biomarkers in numerous thrombo-embolic dis-eases. However, the number of studies evaluating the relationship between these parameters and CVST is very low. Objective: The purpose of this retrospective study was to investigate the relationship between PLR, NLR, and SII values on admission and long-term prognosis in patients with CVST in the acute -sub-acute period. Methods: Fifty-one patients diagnosed with CVST and 51 healthy controls were included in the study. The patient and control groups were compared in terms of NLR, PLR, and SII values. Pa-tients were classified into good and poor prognosis groups based on sixth-month modified Rankin scale scores (mRS) (0-2: good prognosis, 3-6: poor prognosis). Clinical and radiological features and PLR, NLR, and SII values were compared between the good and poor prognosis groups. Multi-variate logistic regression analysis was used to identify independent prognostic factors for poor prognosis. The Receiver Operating Curve (ROC) was used to demonstrate the predictive power of PLR, NLR, and SII. Results: Higher NLR and SII emerged as independent factors for poor prognosis in patients with CVST. NLR was the strongest parameter in predicting poor prognosis in CVST (AUC: 0.817, 95% CI: 0.63-1.00, sensitivity 70%, specificity 92.7%, p:0.002). Conclusion: Higher NLR and SII on admission may be a predictor of long-term poor prognosis in patients with acute-subacute CVST.