Persistent stomach infection with Helicobacter pylori (HP) causes chronic mucosal inflammation (gastritis), an essential precursor to gastric cancer. Genetic polymorphisms in the IL18 gene strongly correlate with an increased risk of atrophic gastritis and gastric cancer, yet the regulation and function of this cytokine in HP inflammation remain poorly understood. It has been reported that the Nod-like receptor protein 3 (NLRP3) mediates secretion of bioactive IL-18 in myeloid cell linages through “inflammasome” assembly upon HP infection. By performing bone-marrow reconstitution studies, however, we identified non-hematopoietic cells as being the major source of IL-18 in the gastric mucosa of HP-infected mice and showed that loss of IL-18 in this cell compartment resulted in mucosal hyperplasia and increased acid mucin production, indicative of early stage intestinal metaplasia. Given that gastric epithelial cells (GECs) highly express the NLR protein NOD1, which detects Gram-negative bacterial peptidoglycan and plays an important role in host immunity against HP infection, we further investigated the involvement of this receptor in HP-associated IL-18 responses. Here, we demonstrated that HP or HP-derived outer membrane vesicles induce mature IL-18 production in both mouse and human GECs. CRISPR/Cas9-mediated gene knockout showed that the HP-induced mature IL-18 secretion is driven by NOD1 receptor which interacts with caspase-1 via its caspase-activation recruitment domain (CARD), resulting in processing of pro-IL-18. Collectively, this is the first study, to our knowledge, reveals an unanticipated function of NOD1 signaling in posttranslational regulation of IL-18 in GEC and an important role for IL-18 in maintaining gastric mucosal homeostasis. These findings suggest a rationale to target this signaling in HP-infected patients to reduce the risks of developing gastric cancer.