Nanomedicines represent innovative and promising alternative technologies to improve the therapeutic effects of different drugs for cancer ablation. Targeting M2-like tumor-associated macrophages (TAMs) has emerged as a favorable therapeutic approach to fight against cancer through the modulation of the tumor microenvironment. However, the immunomodulatory molecules used for this purpose present side effects upon systemic administration, which limits their clinical translation. Here, the biocompatible lignin polymer is used to prepare lignin nanoparticles (LNPs) that carry a dual agonist of the toll-like receptors TLR7/8 (resiquimod, R848). These LNPs are targeted to the CD206-positive M2-like TAMs using the "mUNO" peptide, in order to revert their pro-tumor phenotype into anti-tumor M1-like macrophages in the tumor microenvironment of an aggressive triple-negative in vivo model of breast cancer. Overall, we show that targeting the resiquimod (R848)-loaded LNPs to the M2-like macrophages, using very low doses of R848, induces a profound shift in the immune cells in the tumor microenvironment towards an anti-tumor immune state, by increasing the representation of M1-like macrophages, cytotoxic T cells, and activated dendritic cells. This effect consequently enhances the anticancer effect of the vinblastine (Vin) when co-administered with R848-loaded LNPs.