The forkhead box M1 (FOXM1) transcription factor plays crucial roles in regulating the proliferation, differentiation, and transformation of cells. Overexpression of FOXM1 is associated with a variety of aggressive solid carcinomas, including bladder cancer. However, the precise role and molecular mechanism responsible for the aggressive action of FOXM1 in bladder cancer remain unclear. Real-time quantitative PCR, Western blot and immunohistochemistry were used to explore FoxM1 expression in bladder cancer cell lines, primary bladder cancer clinical specimens and normal bladder tissues. FoxM1 expression was knocked down by small interfering RNA (siRNA) in T24 cells; proliferation, migration and invasion were assayed. FoxM1 expression was up-regulated in the majority of the bladder cancer tissue specimens at both mRNA and protein levels. Immunohistochemistry analysis showed that FoxM1 expression was significantly correlated with TNM stage and histological grade, metastasis. Experimentally, we found that down-regulation of FoxM1 inhibited cell proliferation, migration and invasion. These results suggested that FOXM1 up-regulation was associated with poor prognosis in bladder cancer, and therefore it might act as a prognostic marker and a new potential target for bladder cancer treatment.