Gastrointestinal cancer is a great threat to human health in Japan. Conventional anticancer therapies including surgery, radiation, and chemotherapy are the main strategies and play important roles in curing this disease or extending the life of patients with these cancers. On the other hand, patients undergo great suffering induced by these treatments. Kampo, the Japanese traditional medicine, has been used in clinics to reduce side effects and to improve the quality of life of gastrointestinal cancer patients in Japan. In order to testify to the efficacy and safety of these Kampo medicines and to clarify the underlying mechanisms, a number of clinical and basic studies were implemented in the past several decades. These studies suggested the benefits of Kampo medicine as an adjuvant to conventional anti-cancer therapies in treating gastrointestinal cancer. Since the safety and efficacy as well as quality control of traditional medicine have long been focused worldwide, the development course of Kampo medicine may provide reference to other countries in the world.