The gastrointestinal tract is known as the largest endocrine organ that encounters and integrates various immune stimulations and neuronal responses due to constant environmental challenges. Enterochromaffin (EC) cells, which function as chemosensors on the gut epithelium, are known to translate environmental cues into serotonin (5-HT) production, contributing to intestinal physiology. However, how immune signals participate in gut sensation and neuroendocrine response remains unclear. Interleukin-33 (IL-33) acts as an alarmin cytokine by alerting the system of potential environmental stresses. We here demonstrate that IL-33 induced instantaneous peristaltic movement and facilitated Trichuris muris expulsion. We found that IL-33 could be sensed by EC cells, inducing release of 5-HT. IL-33-mediated 5-HT release activated enteric neurons, subsequently promoting gut motility. Mechanistically, IL-33 triggered calcium influx via a non-canonical signaling pathway specifically in EC cells to induce 5-HT secretion. Our data establish an immune-neuroendocrine axis in calibrating rapid 5-HT release for intestinal homeostasis. Display omitted •IL-33-ST2 signaling regulates gut motility and intestinal host defense•Enterochromaffin (EC) cell-derived ST2 responds to IL-33 for 5-HT release•TRPA1 is required for IL-33-mediated 5-HT release•IL-33 induces PLC-γ1 activation for 5-HT release in both mouse and human EC cells Enterochromaffin (EC) cells are known to act as chemosensors on the gut epithelium, translating environmental cues into serotonin (5-HT) production. Chen et al. demonstrate that an alarmin cytokine IL-33 could be sensed by EC cells, inducing release of 5-HT, regulating intestinal homeostasis and host defense.