Abstract: Kidney injury and decreased chemosensitivity of tumor cells are obstacles with cisplatin (CDDP) chemotherapy. Down-regulation of the organic cation transporter 2 (OCT2) and multidrug resistance-associated protein 2 (MRP2) is a key means to alleviate CDDP-induced kidney injury and increase chemosensitivity. Astragaloside IV (AS IV) is obtained from the well-known traditional Chinese herb Astragalus membranaceus. This study explored the role of AS IV in preventing kidney injury and enhancing the antitumor effect of CDDP by suppressing OCT2 expression in kidney and MRP2 in tumors. This project was reviewed and approved by the Animal Ethics Committee of the First Hospital of Jilin University. The effects of AS IV on CDDP inhibition of tumor growth and promotion of apoptosis were assessed in Lewis lung tumor (LLC)-bearing mice by H&E and TUNEL staining. Kidney injury was assessed by serum biochemical parameters and H&E staining. We used Western blotting and immunohistochemistry assays to detect OCT2 and MRP2 expression in kidney and tumor. The concentration of CDDP in kidney and tumor was measured by HPLC-MS/MS. AS IV enhanced CDDP chemosensitivity by increasing tumor cell apoptosis and slowing tumor growth, and decreased kidney injury as evidenced by lower blood creatinine (Cr) and blood urea nitrogen (BUN). Co-administration of AS IV suppressed MRP2 overexpression induced by CDDP in tumor tissues and may be an important mechanism for enhancing CDDP chemosensitivity. Moreover, AS IV reduced CDDP-induced kidney injury in mice along with suppression of OCT2 expression in kidney. The concentration of CDDP was increased in tumor but decreased in kidney. In total, AS IV not only enhanced the antitumor effect of CDDP by suppressing MRP2 expression in tumor cells, but also decreased kidney injury induced by CDDP. The results provide new insight into the combined use of a chemotherapy drug and natural ingredients to treat cancer.