This study examined the effect of gamma irradiation (3-20 kGy) on the immune activity and physicochemical properties of Myagropsis myagroides (MM) water extracts. MM powder and water extracts were subjected to gamma irradiation at 3, 7, and 20 kGy. The effects of gamma-irradiated MM water extracts on splenocyte proliferation and cytokine IFN-${gamma}$ and IL-2 secretion were evaluated. The gamma-irradiated MM water extracts resulted in decreased splenocyte proliferation without cytotoxicity. The IFN-${gamma}$ and IL-2 secretion increased by gamma-irradiated MM water extracts with increasing irradiation dose. For MM powder, the yield and total phenolic compounds (TPC) of water extracts were increased slightly after gamma irradiation. In MM water extracts, the TPC was higher at a dose of 20 kGy, while gamma irradiation decreased the viscosity, pH, and color of the MM extracts. In conclusion, gamma irradiation improved the immunomodulatory activity of MM water extracts, overcoming its potential weakness when applied in the food industry.