Bladder cancer is one of the most common malignancies of the male genitourinary urinary system. Protodioscin is a steroidal saponin with anti-cancer effects on several types of cancers; however, the anti-cancer activities of protodioscin on bladder cancer have not yet been investigated. Therefore, we aimed to examine the anti-cancer effects of protodioscin on bladder cancer. Two types of bladder cancer cell lines, non-muscle-invasive 5637 cells and muscle-invasive T24 cells, were used to evaluate the effects of protodioscin on cell growth, migration, invasion and epithelial–mesenchymal transition(EMT) marker expressions. Transcriptome analysis was performed by RNA-seq and validated using real-time PCR and western blot; additionally, an in vivo xenograft animal model was established and the anti-tumor effects of protodioscin were tested. Our results demonstrated that protodioscin inhibited cell proliferation, migration, motility and invasion on 5637 and T24 cells. Additionally, protodioscin also induced cell apoptosis and arrested the progression of cell cycle at G2 phase in bladder cancer cells. Moreover, protodioscin inhibited EMT through increased protein expression of E-cadherin and decreased protein expression of N-cadherin and vimentin. RNA-seq analysis indicated that protodioscin regulated mitogen-activated protein kinase(MAPK) and phosphoinositide 3-kinases(PI3K)/protein kinase B(AKT)/mammalian target of rapamycin(mTOR) signaling pathways as further verified by Western blot. Furthermore, protodioscin significantly inhibited tumor growth in vivo. Our results indicated that protodioscin inhibits cell growth, migration and invasion and induces apoptosis and G2 phase cell cycle arrest by activated p38 and JNK signaling pathways in bladder cancer cells, suggesting that protodioscin could be an effective agent for bladder cancer treatment.