Abstract Fucoidan is a series of sulfated polysaccharides derived from brown algae that mainly consist of L-fucose. Various biological activities of fucoidan such as anti-cancer and immune modulatory effects were reported, and our investigation with animal experiments and human trials demonstrated fucoidan from Cladosiphon okamuranus and Undaria pinnatifida effectively augmented anti-tumor immunity in combination with Agaricus blazei mycelium extract. In this study, we evaluated dietary effects of the two types of high-molecular weight fucoidans and the agaricus extract mix (CUA) on achievement of effective tumor vaccination with a tumor antigen gp70 expressed on colon-26 tumor cell line. Balb/c mice were immunized with 0.05 mg gp70 peptide emulsified in complete freund’s adjuvant and intake 1% CUA containing AIN93G diet for 4 weeks. This procedure totally enhanced systemic immune function because splenocytes from the vaccinated mice extensively proliferate in response to concanavalin A-stimulation. The NK cell activity and gp70 peptide-stimulated IFN-gamma production in splenocytes from the vaccinated mice were tended to augment by the CUA feeding. On the other hands, the CUA feeding potentiated the killing activity to colon-26 carcinoma of draining lymph node (LN) cells from the vaccinated mice in association with increase of gp70-specific CD8-positive T cell population. Furthermore, the expressions of MHC class II molecule (I-A/I-E) on CD11c-positive and F4/80-positive populations of LN cells from the vaccinated mice were elevated by the intake of CUA. These results suggested that the CUA feeding potentially support effective induction of anti-tumor immune function by vaccination with tumor antigen peptides.