Objective <p>This study investigates the impact of fucoidan on ferroptosis in colorectal cancer (CRC) cells and analyzes its mechanism of action through the SLC7A11/GPX4 signaling pathway.</p> Methods <p>The HT-29 colorectal cancer cell line was tested using the CCK-8 cytotoxicity assay to assess how different fucoidan concentrations affect cell survival, and the IC₅₀ value was determined. Cell proliferation was evaluated using the colony formation assay, and the ability of cell migration was assessed using both the scratch test and transwell assay. The relative levels of ferrous ion (Fe²⁺), malondialdehyde (MDA), and glutathione (GSH) in the cells were quantified using kits for ferrous ion, MDA, and GSH. Ferroptosis-related gene expression at the mRNA level was identified through qRT-PCR. The levels of proteins related to ferroptosis, including SLC7A11, GPX4, and COX2, were assessed through Western blot. Employs ultra performance liquid chromatography-mass spectrometry (UPLC-MS) to measure the levels of endogenous metabolites within cells, identify potential differential metabolites, and analyze their associated metabolic pathways.</p> Results <p>The results of the CCK-8 assay, colony formation assay, scratch assay and Transwell assay indicated that fucoidan significantly inhibited the proliferation and migration of HT-29 cells (<i>P</i> &lt; 0.01). The results of Fe²⁺, MDA and GSH detection showed that fucoidan was able to raise the levels of Fe²⁺ and MDA (<i>P</i> &lt; 0.01) while reducing GSH (<i>P</i> &lt; 0.01) in HT-29 cells. Further examination using qRT-PCR and Western blot analysis indicated that fucoidan upregulates COX2 mRNA and protein expression while significantly decreasing the levels of SLC7A11 and GPX4 mRNA and protein (<i>P</i> &lt; 0.05, <i>P</i> &lt; 0.01). The results of the metabolomics analysis demonstrate that fucoidan significantly modulates 27 potential differential metabolites. Additionally, an enrichment analysis of the key metabolites influenced by fucoidan indicates that it primarily impacts metabolic pathways such as phenylalanine metabolism, glycerophospholipid metabolism and sphingolipid metabolism.</p> Conclusion <p>Fucoidan induces ferroptosis in colorectal cancer cells, potentially through the regulation of the SLC7A11/GPX4 signaling pathway and associated metabolic pathways, including amino acid and lipid metabolism.</p>