B23, a multifunctional nucleolar protein, is overexpressed in numerous cancers and is associated with tumorigenesis. However, the clinical significance and potential role of B23 in bladder urothelial carcinoma remains to be elucidated. The present study observed that the mRNA and protein expression levels of B23 were increased in bladder cancer cells and tissues. The overexpression of B23 contributed to tumorigenesis and was associated with poor prognosis in bladder cancer patients. Silencing of B23 by short hairpin RNA inhibited tumor cell growth and colony formation. In addition, knockdown of B23 suppressed the phosphorylation of extracellular signal‑regulated kinase (ERK), resulting in the inactivation of the ERK signaling pathway. Therefore, the present study indicated that B23 promotes bladder cancer cell growth via activation of the ERK signaling pathway and is a novel potential biomarker for the diagnosis and prognosis of bladder cancer.