【Objective】 To explore the expression of checkpoint kinase 2 (CHEK2) in clear cell renal cell carcinoma (ccRCC), its association with the clinicopathological features and prognosis, and to predict its relevant molecular signaling pathways and biological functions. 【Methods】 The gene expression data, phenotype data, and corresponding survival information of ccRCC patients were downloaded from TCGA database. The optimal cutoff value of CHEK2 was determined with the "survminer" package. The patients were divided into low and high expression groups, and the association between CHEK2 expression and clinicopathological features was analyzed. The correlation between CHEK2 expression and ccRCC prognosis was evaluated with univariate and multivariate Cox proportional hazard models. The changes of cell signaling pathways involved in different CHEK2 expression levels were explored with gene set variation analysis (GSVA). The correlation between CHEK2 and immune cell infiltration as well as immune checkpoint molecular expression was analyzed. 【Results】 CHEK2 expression was significantly higher in ccRCC tissues than in normal tissues (P<0.01). Higher level of CHEK2 was significantly associated with higher T stage of ccRCC (P<0.01). Kaplan-Meier analysis showed overall survival (OS) of patients with high CHEK2 expression were notably decreased (P<0.001). Univariate and multivariate analyses revealed CHEK2 expression as an independent risk factor of survival (HR=1.950, 95%CI: 1.490-2.570, P<0.001; HR=1.588, 95%CI: 1.185-2.127, P=0.002). GSVA showed that CHEK2 was involved in the following pathways: proximal tubule bicarbonate reclamation, propanoate metabolism, limonene and pinene degradation, fatty acid metabolism, primary immunodeficiency, systemic lupus erythematosus, p53 signaling pathway, homologous recombination, DNA replication and mismatch repair. Correlation analysis suggested that CHEK2 was associated with increased infiltration of multiple immune cells in ccRCC and upregulation of various immune checkpoint molecules. 【Conclusion】 The high level of CHEK2 in ccRCC is an independent predicting factor for poor prognosis. It is probably involved in regulating related events of tumor immune infiltration and may become a new target for ccRCC therapy.