Bladder cancer is the most common malignant tumor of the urinary system. The intention of the present research is to explore the prognostic value and biological function of solute carrier family 12 member 8 (SLC12A8) in bladder cancer. The analysis based on the TCGA and ONCOMINE database revealed that the expression of SLC12A8 in bladder cancer was notably increased compared with the normal group. SLC12A8 expression was notably correlated with the age, pathological stage, T-stage, and lymph node metastasis of bladder cancer patients. Moreover, the patients’ overall survival was notably shorter in the high SLC12A8 group. Compared with the control, SLC12A8 upregulation enhanced the proliferative, invasive, and migratory capacities of bladder cancer cells and promoted the expression of epithelial–mesenchymal transition (EMT) protein markers including β-catenin, vimentin, snail, and slug, while reduced the expression of E-cadherin. In the case of downregulated SLC12A8 expression, the proliferative, invasive, and migratory capacities of bladder cancer cells and the expression of EMT protein markers presented the opposite trend. This study demonstrated that SLC12A8 was highly correlated with oncogenesis and progression of bladder cancer, indicating that SLC12A8 may be a meaningful biomarker for initial diagnosis and early treatment of bladder cancer.