In terms of antitumor effects, once activated, they secrete IFN‐γ/TNF‐α and cytotoxic molecules (GZMB, perforin), directly killing specific tumor cells and enhancing immune surveillance mediated by DCs/NK cells; in terms of protumor effects, under the influence of chronic stimulation, hypoxia, acidic pH, and inhibitory factors, MAIT cells undergo exhaustion and secrete IL‐17/IL‐8/MMPs, which promote tumor proliferation, invasion, and metastasis. The gene discussed is TNF; the disease is neoplasm.