Although impaired gastrointestinal motility from gastric cancer peritoneal metastasis (GCPM) causes extraordinary pain, its cause is unclear. Interstitial cells of Cajal (ICC) are apparently pacemaker cells, and their loss could cause motor dysfunction. In this study, we developed a mouse model for GCPM, and investigated electrophysiological changes in the small intestine and attendant changes in ICC. We found decreased ICC and disrupted electrical rhythm in the model. Pathologic ICC changes were well described. Cancer peritoneal metastasis may impair intestinal myoelectrical activity by damaging ICC and ICC networks. Interstitial cells of Cajal will be a target of palliative treatment and merit further study.