Abstract: Immune checkpoint inhibitors and antibody–drug conjugates are increasingly incorporated into the clinical management of advanced urothelial carcinoma. The immunohistochemical detection of relevant biomarkers facilitates the selection of individualized precision therapies and supports the prediction of therapeutic efficacy. This review summarizes biomarkers associated with the treatment of urothelial carcinoma and the methodologies and clinical applications of immunohistochemical testing, focusing on the correlation between biomarker expression and the divergent differentiation or histological subtypes of urothelial carcinoma.