This study aimed to investigate the effect of fucoidan on the Wnt/β-Catenin pathway using both in-silico molecular docking, molecular dynamics, ADMET analysis (in frizzled-8 receptor and LRP6 coreceptor) and in-vitro experiments using MCF-7 breast cancer cells. Through the molecular docking analysis, the binding energies on the frizzled-8 receptor were -5.6, -5.1, -9.4, and -8.8 kcal/mol, respectively. Meanwhile, those on the LRP6 receptor, were -7.3, -6.2, -10.0, and -9.8 kcal/mol, respectively. The results showed that fucoidan had a favorable binding affinity for both receptors. Furthermore, it was discovered to reduce the interaction and binding affinity between Wnt agonists to frizzled-8 and LRP6 receptors. This reduction was reflected in the change in the binding energy of the fucoidan-Wnt agonist-frizzled 8 and fucoidan-Wnt agonist-LRP6 complexes, which exhibited decreases of -7.0 kcal/mol and -7.8 kcal/mol, respectively. Fucoidan was found stable in complexes with frizzled-8 receptor and co-receptor LRP6. ADMET study showed it's non-carcinogenic and can be distributed in the body. Fucoidan effectively inhibited β-catenin production, a critical factor in the Wnt/β-catenin pathway. The MCF-7 breast cancer cells were treated with fucoidan extract from S. echinocarpum at incubation times of 24, 48, and 72 h, resulting in a reduction of β-catenin levels by 95.19%, 83.88%, and 80.88%, respectively. Fucoidan also shows no significant difference in value compared to fucoidan standard (F. vesiculosus) and doxorubicin. Fucoidan exhibited antiproliferative effects against breast cancer cells, specifically through its modulation of the Wnt/β-Catenin pathway, and held great potential as an herbal anticancer agent.Communicated by Ramaswamy H. Sarma.