Background <p>Fine particulate matter 2.5 (PM_2.5), a key indicator of air pollution, is classified as a human carcinogen. However, the link between air pollution and bladder cancer (BC) progression remains unclear. Dysregulation of the Wingless-related integration site (Wnt)/β-catenin and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathways is a key driver of tumorigenesis in multiple cancers, including BC.</p> Results <p>This study demonstrated that PM_2.5 exposure enhances BC cell migration and invasion. Ribonucleic acid (RNA) sequencing identified the Wnt signaling pathway as a key regulator in PM_2.5-exposed BC cells. Elevated protein levels of Wnt3A, Wnt5A, and β-catenin, along with the nuclear translocation of β-catenin, further highlighted the role of the PM_2.5-activated Wnt/β-catenin pathway in promoting BC progression. The interaction between the Wnt/β-catenin and MAPK/ ERK pathways was examined using inhibitors and shRNAs. MEK or ERK inhibition not only suppressed PM_2.5-induced upregulation of Wnt3A, Wnt5A, and β-catenin nuclear translocation but also significantly reduced the migration and invasion of PM_2.5-exposed BC cells. Both pathways represent promising therapeutic targets, and several existing pathway-specific inhibitors may be repurposed for the future clinical management of PM_2.5-induced BC progression.</p> Conclusions <p>PM_2.5 promotes BC progression through both the MAPK/ERK and Wnt/β-catenin signaling pathways. MEK/ERK inhibition suppressed PM_2.5-induced nuclear translocation of β-catenin, suggesting that the MAPK/ERK pathway functions upstream of the Wnt/β-catenin pathway. This study provides mechanistic insights into how PM_2.5 exposure drives BC progression and offers a potential foundation for developing targeted therapies for PM_2.5-associated BC.</p>