Nature Reviews Cancer, Published online: 27 January 2026; doi:10.1038/s41568-025-00901-zThe conjugation of glycoproteins and glycolipids with the dietary sugar L-fucose is known as fucosylation. In this Progress article, Bitaraf et al. describe the latest work showing how fucosylation is deregulated in cancer, influencing tumour progression and therapeutic responses, and how it might be leveraged to treat cancer.