<p>Glycosylation, a key post-translational modification, plays a pivotal role in cancer progression by influencing critical processes such as protein folding, immune modulation, and intercellular signaling. Altered glycosylation patterns are increasingly recognized as fundamental drivers of tumorigenesis, contributing to key cancer hallmarks like enhanced tumor migration, metastasis, and immune evasion. These aberrant glycosylation signatures not only offer insights into cancer biology but also serve as valuable diagnostic markers and potential therapeutic targets across a range of malignancies. This review explores the mechanisms underlying glycosylation alterations in cancer. We discuss the molecular basis of these changes, including genetic mutations, epigenetic regulation, and oncogene-driven shifts in glycosylation pathways. Additionally, we highlight recent advancements in glycomics research, with a focus on how these alterations influence tumor progression, angiogenesis, and the tumor microenvironment. Furthermore, the review considers the clinical implications of glycosylation changes, including their role in resistance to anti-cancer therapies and their potential as biomarkers for personalized treatment strategies. By bridging fundamental glycosylation research with clinical applications, this review underscores the promise of glycosylation as both a diagnostic tool and a therapeutic target in oncology, offering new avenues for improved patient stratification and precision medicine.</p>