Gastric cancer has a high morbidity and is a leading cause of cancer-related mortality worldwide. Helicobacter pylori (H. pylori) infection is commonly found in the early stage of gastric cancer pathogenesis, which induces chronic gastritis. Artemisinin (ART) and its derivatives (ARTS, artesunate and DHA, dihydroartemisinin), a new class of potent antimalarials, have been reported to exert both preventive and anti-gastric cancer effects. However, the underlying mechanisms of the chemopreventive effects of ART and its derivatives in H. pylori infection induced-gastric cancer are not fully elucidated. We investigated the effects of H. pylori infection in gastric cancer; and the preventive mechanisms of ART, ARTS and DHA. The H. pylori growth was determined by the broth macro-dilution method, and its adhesion to gastric cancer cells was evaluated by using the urease assay. The protein and mRNA levels, reactive oxygen species (ROS) production, as well as the production of inflammatory cytokines were evaluated by Western blot, real-time PCR, flow cytometry and ELISA, respectively. Moreover, an in vivo MNU (N-methyl-N-nitroso-urea) and H. pylori-induced gastric adenocarcinoma mouse model was established for the investigation of the cancer preventive effects of ART and its derivaties, and the underlying mechanisms of action. ART, DHA and ARTS inhibited the growth of H. pylori and gastric cancer cells,suppressed H. pylori adhesion to the gastric cancer cells, and reduced the H. pylori-enhanced ROS production. Moreover, ART, DHA and ARTS significantly reduced tumor incidence, number of tumor nodules and tumor size in the mouse model. Among these three compounds, DHA exerted the most potent chemopreventive effect. Mechanistic studies showed that ART and its derivatives potently inhibited the NF-κB activation. ART, DHA and ARTS have potent preventive effects in H. pylori-induced gastric carcinogenesis. These effects are, at least in part, attributed to the inhibition of NF-κB signaling pathway. Our findings provide a molecular justification of using ART and its derivatives for the prevention and treatment of gastric cancer. Copyright © 2019. Published by Elsevier GmbH.