Non-muscle invasive bladder cancer (NMIBC) accounts for ~70% of all bladder cancers. One of the serious clinical issues related to the management of NMIBC is that it has significant potential to progress to muscle invasive bladder cancer (MIBC) after initial treatments. α‑Klotho (KLα), originally identified as an anti‑aging gene, has recently been reported to have antitumor effects in various malignancies. In contrast, β‑Klotho (KLβ) has been reported to have protumoral functions. However, the associations between KLα/KLβ and the biological behavior of urothelial carcinoma remain unclear. In the present study, we evaluated the association between clinicopathological background factors of NMIBC and the expression levels of KLα or KLβ. A high expression level of KLβ, but not KLα, was an independent predictive factor of short progression‑free survival for NMIBC. An elevated level of KLβ correlated with a higher incidence of lymphovascular invasion (LVI). We added in vitro assays using human bladder cancer cell lines to investigate the role of KLβ. Treatment with exogenous KLβ protein increased the proliferation, migration, transendothelial migration abilities and anchorage‑independent growth of the cell lines. In addition, the KLβ concentration in voided urine samples obtained before initial transurethral surgery was quantitated with enzyme‑linked immunosorbent assay (ELISA). The urine KLβ concentration was found to be higher in patients with bladder cancer than that in healthy volunteers. Our results suggest that KLβ plays important roles in tumor invasion and progression, and its concentration may be a valuable urine‑based marker for the detection of bladder cancer.