Glycosylation in human cholangiocarcinoma (CCA) actively contributes to pathophysiological steps of tumor progression. Of note is the dynamic modification of proteins by O-linked beta-N-acetyl-glucosamine (O-GlcNAcylation) that modulates various tumor-associated biological activities. By using a cutting-edge chemical proteomic methodology for intact glycopeptide analysis, we show herein that O-GlcNAcylation of Keratin 18 (K18) coordinates the tricarboxylic acid (TCA) cycle enzymes, namely isocitrate dehydrogenases (IDHs), to promote CCA progression. Mechanistically, site-specific O-GlcNAcylation of K18 on Ser 30 stabilizes K18, which benefits the expression of cell cycle checkpoints to enhance cell cycle progression and cell growth. Interaction with IDHs down-regulates the level of citrate and isocitrate, while up-regulates the level of α-ketoglutarate (alpha-KG). Our study thus expands the current understanding of protein O-GlcNAcylation, and adds another dimension of complexity to post-translational control over metabolism and tumorigenesis.