Objective: To assess the prognostic value of the systemic immune-inflammation index (SII) in patients with vulvar cancer. Methods: Data of 130 consecutive patients who underwent primary surgical resection for vulvar cancer at the Medical University of Vienna between 1999 and 2018 was retrospectively analyzed. The SII was defined as platelets × neutrophils/lymphocytes as previously described. Its prognostic value on disease-specific survival (DSS) and overall survival (OS) was evaluated by univariate log-rank tests and multivariable cox regression models. Prediction accuracy was assessed by receiver operating characteristics curves and Youden's J statistics. A HosmerLemeshow test was performed to confirm the model's goodness of fit. Results: A pre-therapeutic high serum SII (>866.4) was associated with advanced International Federation of Gynecology and Obstetrics (FIGO)-stage. In univariate survival analysis, a high SII was associated with both DSS (p<0.001) and OS (p=0.001). A multivariate cox regression model confirmed the prognostic value of SII regarding DSS (p<0.001) and OS (p=0.014) independently from patients' age and FIGO stage. Conclusions Pretherapeutic SII may serve as a promising predictor for survival in patients with vulvar cancer. After clinical validation, the SII may be used to improve both pretreatment patient risk stratification and patient counseling.