Transforming growth factor β (TGF-β), interleukin-10 (IL-10), and vascular endothelial growth factor (VEGF) are three of the commonly studied cytokines playing an important role in tumor initiation and progression. Besides their promotional effects on tumor progression, the three cytokines have immunosuppressive effects that facilitate tumor initiation and progression as well. Ganoderma lucidum polysaccharides (Gl-PS) with multiple bioactivities may have the effect on B16F10 melanoma cells to induce stronger antitumor immune response that has been demonstrated. Gl-PS may have the suppressive effects on the production of these three cytokines, which has yet to be demonstrated. In this study, we tested these effects of Gl-PS by incubating Gl-PS with malignant tumor cells such as B16F10 cells, a melanoma cell line, and LA795 cells, a lung carcinoma cell line. RT-qPCR and enzyme-linked immunosorbent assay showed that the production of TGF-β1, IL-10, and VEGF in B16F10 melanoma cells and LA795 lung carcinoma cells was suppressed by Gl-PS at both mRNA and protein levels, suggesting that the suppression on production of TGF-β, IL-10, and VEGF in B16F10 melanoma cells and LA795 lung carcinoma cells by Gl-PS may contribute to the therapy on melanoma and lung carcinoma along with the induction of stronger antitumor immune response.