The proto-oncogene MDM2 is a nuclear-localized E3 ubiquitin ligase, which promotes tumor formation by targeting tumor suppressor proteins, such as p53, for proteasomal degradation. In this study, the anti-infective drug nitroxoline (NXQ) was screened out to effectively inhibit cell survival of small-cell lung cancer (SCLC) cells, and induce SCLC cell apoptosis by suppressing antiapoptotic proteins (such as Bcl-2 and MCL1) and upregulating proapoptotic protein Bim. In the mechanistic study, NXQ was found to downregulate MDM2 expression by inducing its proteasomal degradation, and thus upregulated p53 expression, which was a substrate protein of MDM2. Moreover, overexpression of MDM2 decreased the cytotoxicity of NXQ on SCLC cells. These results demonstrated that NXQ displayed anti-SCLC activity by suppressing MDM2 expression, which suggested that anti-infective NXQ had potential for SCLC treatment by targeting the MDM2/p53 axis.