STK11 is a frequently mutated tumor suppressor in lung adenocarcinoma (LUAD). STK11 mutations also lead to dramatic changes in the tumor microenvironment. Studies have shown that strengthening the killing effect of NK cells is vital for effective cancer treatment. Nonetheless, the mechanism of STK11 mutation in modulating the killing effect of NK cells on LUAD cells remains unclear. The expression of STK11, Ki67, and IFN-γ in tumor tissues was evaluated by immunohistochemistry. The contents of T cells, NK cells, and macrophages were analyzed by immunofluorescence assay. The expression of IL2, IL6, and IFN-γ was detected by ELISA. STK11 expression in LUAD cell line was evaluated by qRT-PCR. CCK-8 and colony formation assay were used to measure proliferative ability of LUAD cells and the viability of NK cells. Flow cytometry was utilized to analyze cell apoptosis and NK cell content. Transwell assay was utilized to measure the chemotactic capability of NK cells. In vivo experiments validated the effect of abnormal expression of STK11 on tumor growth. LUAD patients with STK11 mutation had a high tumor proliferative ability. Forced expression of STK11 could substantially constrain the proliferation of LUAD cells and induce cell apoptosis. In addition, STK11 deletion significantly reduced the infiltration level of NK cells and inhibited the viability and chemotactic ability of NK cells as well as their killing effect on LUAD cells. In vivo animal experiment results demonstrated that STK11 deletion significantly reduced NK cell infiltration and promoted LUAD tumor growth. This study revealed the mechanism of STK11 mutation regulating NK cytotoxicity and promoting tumor development, providing scientific basis for the exploration of STK11-related LUAD therapeutic targets and theoretical reference for developing new NK cell-based immunotherapy.