Sea cucumbers are used as healthy food, traditional medicine and dietary supplement. Sulphated polysaccharides (sPS) from their body wall possess variety of biological activities; however the immunomodulatory effects of sea cucumber polysaccharides remain unknown. Three sPS fractions were isolated from orange-footed sea cucumber (Cucumaria frondosa) and their effects on DC maturation investigated. DCs, matured in the presence of high molecular-weight FCF-1 (100 and 1000 µg/ml) with a monosaccharide composition of NANA, GlcNAc, Man, Gal, Fuc and GalNAc (40:13:12:12:9:8:3), secreted reduced levels of IL-10, IL-12p40 and IL-6 (only at 1000 µg/ml). Furthermore, allogeneic CD4+ T cells co-cultured with DCs matured with FCF-1 (100 µg/ml) secreted reduced levels of IFN-γ and increased levels of IL-17 than allogeneic CD4+ T cells co-cultured with DCs matured without FCF-1. These data suggest that FCF-1 can affect the DC maturation leading to increased Th17 and reduced Th1 activity; thus, increasing the Th17-mediated defence against yeast and extracellular bacteria.