Background: Chemoresistance is a major obstacle to successful chemotherapy for human non-small cell lung cancer (NSCLC). Astragaloside IV, the component of Astragalus membranaceus, has been reported to exhibit anti-inflammation, anti-cancer and immunoregulatory properties. In the present study, we investigated the role of astragaloside IV in the chemoresistance to cisplatin in NSCLC cells. Methods: We established astragaloside IV-suppressed NSCLC cell lines including A549, HCC827, and NCI-H1299 and evaluated their sensitivity to cisplatin in vitro. In addition, we examined the mRNA and protein levels of B7-H3 in response to cisplatin-based chemotherapy. Results: We showed that high doses of astragaloside IV (10, 20, 40 ng/ml) inhibited NSCLC cell growth, whereas low concentrations of... astragaloside IV (1, 2.5, 5 ng/ml) had no obvious cytotoxicity on cell viability. Moreover, combined treatment with astragaloside IV significantly increased chemosensitivity to cisplatin in NSCLC cells. On the molecular level, astragaloside IV co-treatment significantly inhibited the mRNA and protein levels of B7-H3 in the presence of cisplatin. In addition, ectopic expression of B7-H3 diminished the sensitization role of astragaloside IV in cellular responses to cisplatin in NSCLC cells. Conclusion: These results demonstrate that astragaloside IV enhances chemosensitivity to cisplatin via inhibition of B7-H3 and that treatment with astragaloside IV and inhibition of B7-H3 serve as potential therapeutic approach for lung cancer patients.