This study aimed to further validate the prognostic role of fibrinogen in upper tract urothelial carcinoma (UTUC) in a large Chinese cohort. A total of 703 patients who underwent radical nephroureterectomy were retrospectively identified. Fibrinogen levels of ≥4.025 g l-1 were defined as elevated. Logistic regression analysis was performed to determine the association between fibrinogen and adverse pathological features. Kaplan-Meier analysis and Cox regression models were used to assess the associations of fibrinogen with cancer-specific survival (CSS), disease recurrence-free survival (RFS), and overall survival (OS). Harrell c-index and decision curve analysis were used to assess the clinical utility of multivariate models. The median follow-up duration was 42 (range: 1-168) months. Logistic regression analysis revealed that elevated fibrinogen was associated with higher tumor stage and grade, lymph node involvement, lymphovascular invasion, sessile carcinoma, concomitant variant histology, and positive surgical margins (all P < 0.05). Multivariate Cox regression analysis demonstrated that elevated fibrinogen was independently associated with decreased CSS (hazard ratio [HR]: 2.33; P < 0.001), RFS (HR: 2.09; P < 0.001), and OS (HR: 2.09; P < 0.001). The predictive accuracies of the multivariate models were improved by 3.2%, 2.0%, and 2.8% for CSS, RFS, and OS, respectively, when fibrinogen was added. Decision curve analysis showed an added benefit for CSS prediction when fibrinogen was added to the model. Preoperative fibrinogen may be a strong independent predictor of worse oncologic outcomes in UTUC; therefore, it may be valuable to apply this marker to the current risk stratification in UTUC.