Abstract: There is an obvious urgent need to find effective and safe therapies to prevent both recurrence and progression of bladder cancer. In the present study, we report that fisetin-induced apoptosis in human bladder cancer is mediated via modulation of two related pathways: up-regulation of p53 and down-regulation of NF-kappa B activity, causing a change in the ratio of pro- and anti-apoptotic proteins. The results showed that fisetin inhibited the proliferation of T24 and EJ cells by inducing apoptosis and blocking cell cycle progression in the G0/G1 phase. Western blot assay showed that fisetin significantly increases the expression of p53 and p21 proteins, and decreases the levels of cyclin D1, cyclin A, CDK4 and CDK2, thereby contributing to cell cycle arrest. In addition, fisetin increased the expression of Bax and Bak but decreased the levels of Bcl-2 and Bcl-xL and subsequently triggered mitochondrial apoptotic pathway. Our study suggests that the activation of p53 and inhibition of the NF-kappa B system may play important roles in the fisetin-induced apoptosis in bladder cancer cells.