Background Bladder cancer (BC) is a common urologic malignancy with high recurrence and progression rates, and outcomes for advanced disease remain poor. Peroxisome proliferator-activated receptor gamma (PPARγ) is involved in tumor metabolism and progression, but its role in BC is not fully defined.Methods We investigated the effects of 15dPGJ2, alone or in combination with cisplatin, on bladder cancer cells using a series of functional assays in T24 and RT4 cell lines and further validated the antitumor effects in a xenograft mouse model.Results Analysis of The Cancer Genome Atlas (TCGA) dataset revealed that higher PPARγ expression is associated with improved overall survival in BC patients. Treatment with 15-deoxy-Δ¹²,¹⁴-prostaglandin J₂ (15d-PGJ2), a natural PPARγ ligand, significantly suppressed cell viability and colony formation in T24 and RT4 bladder cancer cells. Mechanistically, 15d-PGJ2 induced mitochondrial oxidative stress, as demonstrated by increased mitochondrial reactive oxygen species (ROS), elevated JC-1 green/red fluorescence ratios, and mitochondrial depolarization and fragmentation. These changes were accompanied by reduced mitochondrial length and downregulation of mitochondrial dynamics and respiratory proteins, including Tom20, MFF, COX IV, and ATP5A, along with increased p-Drp1 and cleaved PARP expression. Combined treatment with cisplatin and 15d-PGJ2 further enhanced mitochondrial dysfunction and ROS production, resulting in synergistic inhibition of cell viability. In a T24 xenograft mouse model, 15d-PGJ2 alone or in combination with cisplatin significantly reduced tumor growth, as confirmed by IVIS imaging, histological analysis, and immunohistochemistry, with tumor tissues showing increased apoptosis and suppression of mitochondrial-related proteins.Conclusion 15d-PGJ2 inhibits bladder cancer growth by inducing mitochondrial oxidative stress and dysfunction and represents a promising mitochondrial-targeting chemosensitizer for bladder cancer therapy.