<p>Recent studies highlight the multifaceted roles of neurotransmitters in tumor immunomodulation, offering novel avenues for increasing therapeutic efficacy. These signaling molecules are classified into cholinergic agents, monoamines, amino acids, and peptides and regulate tumorigenesis, metastasis, and immune evasion via autocrine/paracrine pathways and receptor-mediated interactions. Notably, neurotransmitters influence tumor cell proliferation, apoptosis, and immune cell activity by modulating intracellular signaling cascades through posttranslational modifications (serotonylation and dopaminylation). Emerging evidence highlights their dual roles: serotonin enhances glycolysis in CD8⁺ T cells to potentiate antitumor responses, while γ-aminobutyric acid accumulates in tumors to promote immune escape. Pharmacological interventions targeting neurotransmitter synthesis, release, or receptor signaling, such as combining antagonists with immune checkpoint inhibitors, result in improved clinical outcomes. Additionally, neurotransmitter-driven tumor vaccines represent a promising frontier. This review synthesizes mechanistic insights into the neurotransmitter-mediated regulation of the tumor microenvironment and proposes innovative strategies to optimize immunotherapy by exploiting neuromodulatory pathways. These findings provide a translational framework for developing precision therapies that integrate neuroimmune crosstalk in oncology.</p>