Macrophage polarization is a pivotal determinant in the modulation of immune responses and the formation of the tumor-microenvironment (TME), therefore represents a promising avenue for the development of cancer immunotherapy. Recent research highlights the potential of edible mushroom polysaccharides in inducing M1/M2 polarization of macrophages. Here, we report that oral administration of Flammulina (F.) velutipes polysaccharide (FVP) reduced the tumor volume of grafted 4T1 mammary and lewis lung carcinoma (LLC), and increased the overall survival rate of mice. Moreover, this polysaccharide induced the generation of CD11b⁺Ly6C^highF4/80⁺ macrophage cells in LLC and 4T1 tumor-bearing mice. Further investigation found that FVP decreased the ratio of M2-macrophages and regulatory T cells in TME, which is known to support tumor growth and metastasis. Mechanistically, FVP reversed the IL-4 induced M2-polarization by activating the TLR4/ NF-κB axis, and in vitro assays confirmed the expression of pro-inflammatory genes and the antitumor effects of the polysaccharide. Additionally, the expression of Th1 response relative genes also enhanced by FVP polarized macrophage secretions. In summary, these results suggest that FVP may represent a promising immunomodulatory agent for the reversal of macrophage polarization.