Treatment with kampo, the Japanese traditional medicine, is a form of pharmacological therapy that combines modern Western and traditional Asian medical practices. In Japan, various traditional medicines are often combined with Western medicines and prescribed for patients with diseases such as gastroesophageal reflux disease, functional dyspepsia, chronic gastritis, irritable bowel syndrome, and post-operative ileus. Based on numerous past observations, Japanese traditional medicines are thought to be particularly useful in the treatment of medically unexplained physical symptoms such as nausea, abdominal discomfort, and anorexia. However, the detailed mechanism by which they mediate their pharmacological action is yet unknown. In addition, the clinical evidence to support their use is insufficient. This review focuses on the basic evidence of the pharmacological action and the clinical efficacies of kampo medicines accumulated over several past decades. In addition, we introduce both the current novel insights into kampo medicines and the therapeutic approach employed when they are used to treat various disorders of the gastrointestinal tract.