Neoantigen-based tumor vaccines have been applied in patient-specific melanoma-derived immunogenic mutated epitopes (neoantigens), with potential antineoplastic and immunomodulating effects. Yet, their use is limited by different physicochemical properties and poor pharmacokinetics. Herein, we constructed a human serum albumin-based dual adjuvant neoantigen nanovaccine loaded with imiquimod and magnesium. Magnesium, in coordination with imiquimod, could greatly activate dendritic and T cells. After subcutaneous injection, the nanovaccine effectively targeted tumor-draining lymph nodes (LNs) and promoted the presentation of neoantigens, thus generating a large number of effector T cells. In the B16F10 mouse melanoma prevention model, the nanovaccine effectively inhibited tumor growth and prolonged the survival time of tumor-bearing mice. To sum up, this new neoantigen nanovaccine could be used as a new method for targeting melanoma and may be potentially applied in clinical work.