Galectin-9 (Gal-9), a member of animal lectin family with evolutionary conserved carbohydrate recognition domains, has been reported to exert a large variety of functional roles in tumorigenesis due to its β-galactoside-binding affinity. The aim of this study is to evaluate the expression and prognostic significance of Gal-9 in patients with clear-cell renal cell carcinoma (ccRCC). The expression of Gal-9 was assessed by immunohistochemistry in 196 patients with ccRCC who underwent nephrectomy. In the cohort, 48 patients died and 61 patients suffered recurrence. Kaplan-Meier method with log-rank test was applied to compare survival curves. The authors employed univariate and multivariate Cox regression models to evaluate the prognostic value of Gal-9 expression in overall survival (OS) and recurrence-free survival (RFS). In patients with ccRCC, Gal-9 expression, which was positively associated with tumor size (P = 0.014), Fuhrman grade (P = 0.010), and necrosis (P = 0.025), was determined to be an independent prognostic indicator for OS (hazard ratio [HR] 2.394; P = 0.005) and RFS (HR 2.096; P = 0.006). High expression of Gal-9 was associated with poor survival (P = 0.001) and early recurrence (P = 0.006). Furthermore, Gal-9 expression could significantly stratify the patients in early (grades I + II) tumor, node, and metastasis (TNM) stage (OS: P = 0.005; RFS: P = 0.041) and low (grades 1 + 2) Fuhrman grade (OS: P = 0.004; RFS: P = 0.006). The prognostic accuracy of TNM, SSIGN, and UISS prognostic models was improved when Gal-9 expression was added. Gal-9 expression is a potential independent prognostic factor for OS and RFS in patients with ccRCC.