Taxol is an anti-cancer agent that stabilizes the microtubules of cancer cells, resulting in inhibition of mitosis and thus preventing the proliferation of cancer cells. However, many anti-cancer agents including taxol work on normal cells as well as cancer cells, resulting in side effects such as immunosuppression. A marine algae-derived sulfated polysaccharide, fucoidan, an anti-cancer agent, also showed immunostimulating effects. This study investigated the effects of fucoidan on taxol-treated spleen cells. Spleen cells were treated with taxol in a concentration-dependent manner and in combination with fucoidan. MTT assay and flow cytometry analysis were performed to measure the viability and activity of treated cells. Two assays demonstrated that taxol induced the death of spleen cells. Fucoidan clearly inhibited the cell death induced by taxol. In addition, fucoidan enhanced the production of nitric oxide in spleen cells, which was decreased by taxol. Taken together, taxol can induce the cell death of spleen cells, a major type of immune cells and fucoidan protects spleen cells from taxol-induced cell death. This finding suggests that taxol and fucoidan can be used in combination for lowering the immunosuppressive effects of taxol.