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Acquired resistance to Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as gefitinib, remains a major therapeutic challenge in EGFR-mutant non-small cell lung cancer (NSCLC). Here, we report that cepharanthine (CEP), a natural bisbenzylisoquinoline alkaloid, effectively reverses gefitinib resistance through concurrent suppression of the AKT/P70S6K survival axis and activation of the Stimulator of Interferon Genes (STING)-mediated innate immune pathway. In gefitinib-resistant H1975 cells (EGFR L858R/T790M), CEP monotherapy significantly inhibited proliferation and induced mitochondrial apoptosis. Notably, CEP synergized with gefitinib to enhance therapeutic efficacy. RNA sequencing and functional validation revealed that CEP activates the STING/TANK-Binding Kinase 1 (TBK1)/Interferon Regulatory Factor 3 (IRF3) signaling cascade, resulting in robust production of T-cell chemoattractants C-X-C Motif Chemokine Ligand 9 (CXCL9), C-X-C Motif Chemokine Ligand 10 (CXCL10), and C-C Motif Chemokine Ligand 5 (CCL5). Critically, the STING inhibitor H-151 abolished CEP's antitumor effects in vitro. Our findings reveal a novel dual mechanism action of CEP and nominate it as a potential candidate for overcoming TKI resistance in NSCLC.