Objective To explore the effect of versican (VCAN) gene on immunocyte infiltration and prognosis of bladder urothelial carcinoma (BUC). Methods The high-throughput sequencing data and clinical data of BUC were downloaded from TCGA database. The correlation between the expression level of VCAN and clinical characteristics of BUC patients was analyzed using the Limma R package; univariate and multivariate Cox regression analysis were performed to analyze the effect of VCAN expression and clinical characteristics (including gender, age, tumor grade, tumor stage, lymph node metastasis and distant metastasis) on the prognosis of BUC patients; TIMER database was used to analyze the correlation between VCAN expression level and immunocyte infiltration. T24 cells were divided into three groups: control group (cells transfected without any siRNA), NC siRNA group (cells transfected with negative control siRNA), and VCAN siRNA group (cells transfected with VCAN siRNA). After transfection, the proliferation, invasion and cell cycle proportion of T24 cells were determined by MTT assay, Transwell assay and flow cytometry, respectively. The protein expression levels of Cyclin E, Cyclin D1, E-cadherin and matrix metalloproteinase-9 (MMP-9) were determined by Western blotting. Results Compared with normal bladder tissues, the expression level of VCAN mRNA in BUC tissues was significantly up-regulated, and was positively correlated with tumor grade, tumor stage and distant metastasis (P<0.01). High VCAN expression was an independent risk factor for poor prognosis in BUC patients (P<0.05). The results of TIMER database analysis showed that the expression level of VCAN was significantly positively correlated with the infiltration degree of macrophages and regulatory T cells in BUC (P<0.001). Compared with control group, the proliferation and invasion ability of T24 cells in VCAN siRNA group decreased significantly and the cell proportion of G₀/G₁ phase increased significantly (P<0.05), the protein expression levels of Cyclin E, Cyclin D1 and MMP-9 were down-regulated significantly, and of E-cadherin was up-regulated significantly (P<0.05). Conclusions VCAN is highly expressed in BUC and correlated with immune infiltration and prognosis of BUC. Silencing the expression of VCAN may significantly inhibit the proliferation and invasion of T24 cells by regulating the protein expression levels of Cyclin E, Cyclin D1, E-cadherin and MMP-9.