Background: Oridonin is a Chinese herbal medicine exhibiting anti-tumor properties; however, its immune modulation capacity has yet to be elucidated. Our objective in this study was to determine whether oridonin enhances the anti-tumor activity of natural killer (NK) cells against lung cancer cells. Methods: LDH-releasing assays were used to investigate the effects of oridonin on NK-92MI cell activity against lung cancer cells. Flow cytometry and real-time PCR were used to examine the effects of oridonin on degranulation markers, cytotoxic factors, activating receptors on NK-92MI cells, and ligands in lung cancer cells. Western blot analysis provided insight into the mechanisms underlying the observed effects. Results: Oridonin enhanced the cytotoxic effects of NK-92MI cells against A549 lung cancer cells. This effect involved upregulating the expression of the degranulation marker CD107a and IFN-γ as well as activating receptors on NK cells and their ligand MICA/B. Oridonin also inhibited STAT3 phosphorylation in A549 cells and NK-92MI cells. A lung cancer mouse model confirmed the anti-tumor effects of oridonin and NK-92MI cells, wherein both treatments alone suppressed tumor growth. Oridonin was also shown to have a synergistic effect on the anti-tumor activity of NK-92MI cells. Conclusions: The ability of oridonin to enhance the cytotoxic effects of NK cells indicates its potential as a novel therapeutic agent for the treatment of lung cancer.Keywords: Anticancer effect; Lung cancer; Natural killer cell; Oridonin.