The maximally tolerated dose (MTD) approach in conventional chemotherapy accompanies adverse effects, primarily due to high drug concentrations in the blood after intravenous administration and non-specific damages to highly proliferating cells, including immune cells. This causes the immune system to dysfunction. To rather boost intrinsic tumor-fighting immune capacity, we demonstrate a new oral route treatment regimen of docetaxel (DTX) without apparent toxicity. The DTX-loaded cationic solid lipid nanoparticles (DSLN-CSG) were coated with an anionic polymer conjugated with glycocholic acid. The resulting nanoparticles (DSLN-CSG, ~120 nm in diameter) were actively absorbed in the distal ileum mediated by interactions with the apical sodium bile acid transporter. The plasma DTX profile was sustained up to 24 h after a single oral dose and did not impair the functions of the immune system. In mouse models, daily oral DSLN-CSG administration inhibited the growth of existing tumors and tumor formation by medication prior to cancer cell inoculation. The extent of effects depended on the cancer cell lines of melanoma, colorectal adenocarcinoma, and breast carcinoma. It was most effective for melanoma in growth inhibition and in preventing tumor formation in mice. During the medication, the cytotoxic T cell population increased while the populations of tumor-associated macrophage and regulatory T cell declined. The low dose daily oral treatment may help patients with intermittent maintenance therapy between MTD cycles and prevent tumor recurrence after completing remission for certain tumors.