Nucleotide metabolism reprogramming is a hallmark of cancer, yet its systematic investigation remains limited. Here, we performed a comprehensive multi-omics analysis of key nucleotide metabolism genes across various cancer types using TCGA, GTEx, and other public datasets. Uridine-cytidine kinase 2 (UCK2), a key enzyme in the pyrimidine salvage pathway, was identified as consistently upregulated and genomically amplified, particularly in bladder cancer (BLCA). High UCK2 expression in BLCA correlated with poor prognosis, advanced tumor stage, high-grade histology, and strong diagnostic performance (AUC = 0.932). Single-cell and spatial transcriptomic analyses revealed that UCK2 is predominantly expressed in malignant and stromal cells. Functional enrichment analysis linked UCK2 to cell cycle progression, DNA repair, tumor invasion, and immune modulation. UCK2 expression was associated with immune cell recruitment and activation, as well as the expression of immune-related factors, including antigen presentation molecules and immune checkpoints. Higher UCK2 expression also showed a strong correlation with immunotherapy response in anti-PD-L1-treated cohorts. Drug sensitivity profiling indicated that UCK2 expression correlates with increased sensitivity to chemotherapeutic agents, such as cisplatin, docetaxel, and gemcitabine. In vitro, CRISPR-Cas9-mediated knockdown of UCK2 significantly inhibited BLCA cell proliferation, migration, and clonogenicity, while suppressing activation of the PI3K/AKT/mTOR signaling pathway. Collectively, our findings identify UCK2 as a key regulator of tumor progression, metabolic remodeling, and immune interaction in BLCA, highlighting its potential as a diagnostic biomarker and therapeutic target.