Pneumatosis cystoides intestinalis (PCI) is a rare condition in which pneumocysts develop in the submucosa or subserosa of the colon. We report herein a case of PCI induced by the alpha-glucosidase inhibitor (alphaGI) miglitol. There have been 9 recorded cases of PCI induced by other alphaGIs, but this is the first report of miglitol causing PCI. The PCI lesions in our case were smaller than those induced by voglibose or acarbose. The possibility of PCI should be considered in diabetic patients on alphaGI therapy who complain of gastrointestinal symptoms, and the gastrointestinal tract should be thoroughly investigated in these patients.