LCMV gp 33-41, a viral peptide that evokes an immune response from cytotoxic T cells, was integrated into composite polymeric nanoparticles (NPs) for immune-chemo combination cancer therapy. Doxorubicin and LCMV gp 33-41 were assembled with heparin into a single structure through electrostatic interaction. Pluronic coating was applied to this nanoparticle via freeze-drying. The antitumor efficacy of these NPs was evaluated by measuring the volume of B16F10 melanoma in mice and the survival rate over time. The reduction of cardiotoxicity was also evaluated by measuring cTnT concentration using the ELISA method.