A key issue in dendritic cell (DC)-based cancer immunotherapy is the effective delivery of tumor-specific antigens to DCs. To deliver antigens, non-viral vaccine system has been used in ex vivo manipulation. However, ex vivo manipulation is time-consuming, lacks quality control of DCs, and demonstrates low antigen delivery efficiency, which implicates that there are serious problems in therapeutic DC preparations. Therefore, we developed mannose (MN)-labeled poly(d, l-lactide-co-glycolide) (PLGA) nanoparticles (MN-PLGA-NPs) encapsulating tumor-specific antigens for targeted delivery to mannose receptors (MN-R) on DC surfaces without ex vivo manipulation. The MN-PLGA-NPs showed DC-selective delivery in tumor-bearing mice, leading to highly mature and activated DCs, which migrated to lymphoid organs, resulting in activation of cytotoxic CD8+ T cells. Additionally, MN-PLGA-NPs showed significant therapeutic efficacy in EG7 lymphoma tumorbearing mice. Our nano-platform technology can be used as a vaccine system to bypass ex vivo manipulation and enhance targeted delivery of tumor-specific antigens to DCs, which is well-suited for cancer immunotherapy.