The present study demonstrated the effect of fucoidan, isolated from Fucus vesiculosus, on cell growth and apoptosis in anaplastic thyroid cancer cells. The cell viability was analyzed using a Cell Counting Kit‑8 cell proliferation kit. Diamidino-2-phenylindole and terminal deoxynucleotidyl transferase-mediated dUTP nick‑end labeling assays were used to examine the apoptotic effect of fucoidan, which revealed the presence of apoptotic bodies and DNA fragmentation. Fucoidan inhibited the growth of FTC133 and TPC1 ATC cells in a dose‑dependent manner. It also induced the apoptosis of FTC133 cells by promoting the expression levels of cleaved poly ADP‑ribose polymerase and caspase‑3. Significant decreases in the levels expression of hypoxia-inducible factor 1α and vascular endothelial growth factor were observed in the FTC133 cells following treatment of the cells with fucoidan. In addition, inhibition in tube formation and the migration of FTC133 cells were observed in the cells treated with fucoidan, compared with the cells in the control group. Therefore, fucoidan inhibited cell growth, induced apoptosis and suppressed angiogenesis in the thyroid cancer cells.