Neurodevelopmental disorders often accompany gastrointestinal symptoms such as diarrhea and abdominal pain. Focusing on the irritable bowel syndrome (IBS), a typical disease that manifests gastrointestinal symptoms, we investigated seven cases of neurodevelopmental disorders with IBS that met the diagnostic criteria of Rome III to clarify inducing factors, clinical courses and prognosis. The period from the time of diagnosis of seven cases of neurodevelopmental disorder to the onset of ISB was from 2 months to 11 years and 8 months, and in all cases ISB symptom developed in adolescence. In five out of seven cases, the cause of IBS onset was estimated at activities in school, and in three out of five cases, the symptoms were ameliorated or cured by improvement of onset factors. From the viewpoint that IBS is a psychosomatic disorder, not only a psychological point of view but also a comprehensive support effort was also considered important.