Cancer immunity is mediated through the effective priming and activation of tumor-specific class I major histocompatibility complex (MHC-I) molecule-restricted CD8+ cytotoxic T lymphocytes (CTLs). DEC-205+ dendritic cells (DCs) can cross-present the epitope(s) of captured tumor antigens associated with class I MHC molecules alongside co-stimulatory molecules to prime and activate tumor-specific CD8+ CTLs. Immunosuppressive tolerogenic DCs with reduced co-stimulatory molecules may be a cause of insufficient CTL induction. Hepa1-6-1 cells were established from the mouse hepatoma cell line Hepa1-6; these cells grow continuously after subcutaneous (s.c.) implantation into syngeneic C57BL/6 (B6) mice and do not prime CD8+ CTLs. Here, we show that the growing of tumors was suppressed by activated CD8+ CTLs with tumor-specific cytotoxicity through the administration of the glycolipid α-galactosylceramide (α-GalCer), which is a compound known to stimulate invariant natural killer T (iNKT) cells and selectively activate DEC-205+ DCs. Moreover, we demonstrated that sequential repetitive intraperitoneal (i.p.) inoculation of α-GalCer every 48 hour appeared to convert tolerogenic DEC-205+ DCs into immunogenic DCs with a higher expression of co-stimulatory molecules and a greater cross-presentation capacity, which primed CTL precursors and induced tumor-specific CD8+ CTLs within the tumor environment without activating iNKT cells. These findings provide a new basis for cancer immunotherapy to convert tolerogenic DEC-205+ DCs within tumors into immunogenic DCs via the sequential administration of an immuno-potent lipid/glycolipid, and activated immunogenic DCs with sufficient expression of co-stimulatory molecules prime and activate tumor-specific CD8+ CTLs within the tumor to control tumor growing.