Purpose <p>The transcription factor EBF3 is frequently downregulated in lung adenocarcinoma (LUAD), and its low expression is associated with poor patient prognosis. The functional significance and mechanistic basis of EBF3 in LUAD pathogenesis, particularly its potential impact on the tumor immune microenvironment, remain largely unexplored.</p> Methods <p>A series of in vitro and in vivo assays were performed. Cell proliferation and apoptosis were assessed using CCK-8 and flow cytometry. Signaling pathways were analyzed by Western blot. A syngeneic mouse model was established to evaluate tumor growth and immune cell infiltration by flow cytometry. Macrophage polarization was examined using conditioned medium co-culture assays. The key secreted factor was identified through cytokine screening and validated by rescue experiments.</p> Results <p>EBF3 overexpression significantly suppressed LUAD cell proliferation and induced apoptosis, while its knockdown promoted growth. Mechanistically, EBF3 inhibited the phosphorylation of AKT and P38. In vivo, EBF3 overexpression restricted tumor growth, reduced M2-like macrophage infiltration, and increased CD4⁺ and CD8⁺ T cell recruitment. This immunomodulation was mediated through transcriptional repression of CCL24. Conditioned medium from EBF3-expressing cells inhibited M2 macrophage polarization, and this effect was reversed by exogenous CCL24. Crucially, CCL24 administration rescued the tumor-suppressive and immune-modulatory effects of EBF3 in vivo.</p> Conclusions <p>Our study identifies EBF3 as a pivotal tumor suppressor in LUAD that operates through a dual mechanism: direct suppression of tumor cell growth via AKT/P38 signaling and remodeling of the immune microenvironment via CCL24 repression. The EBF3-CCL24 axis represents a promising therapeutic target for LUAD treatment.</p>