OBJECTIVE: Lactylation is a type of chemical modification involving the introduction of lactyl groups to a molecule which can affect the interactions between tumor cells and their microenvironment. This study aims to evaluate the possible role of lactylation-related gene signature in the prediction of both prognosis and immunotherapy response in bladder cancer (BLCA). METHODS: Lactylation-related genes were obtained from the published work and two subtypes (cluster A and B) were identified through unsupervised clustering. The differences including clinical features, differentially expressed genes (DEGs), pathways, and immune cell infiltration between these two clusters were thoroughly examined. RESULTS: By utilizing the DEGs between the two clusters, a lactylation score was identified to predict the overall survival status and the response of BLCA patients receiving immunotherapy. Our results demonstrated that patients with a high lactylation score tended to have a worse survival period and increased immune cell infiltration level. Further analysis showed that high lactylation score may be associated with higher sensitivity to immune checkpoint inhibitor (ICI) treatment which is crucial in the identification of the suitable candidates for ICI therapy. CONCLUSIONS: Our results emphasize the possible predictive role of lactylation-related gene signature both in the survival rates of BLCA and its implications for treatment strategies.