The government of Japan, from the late 1960s to the first half of the 1970s, considered creating a new international organization called the Asian Medical Organization or the Southeast Asian Medical and Health Organization as part of its efforts to promote international cooperation toward the Southeast Asian nations. This idea was quite ambitious since it included the establishment of a multinational medical university. However, the Japanese all-out diplomatic attempts failed due to the lack of adequate support from these nations. Despite the unsuccessful outcome, this endeavor left the Japanese government with a few lessons and legacies. This paper examines the backdrop of the concept of building a new international organization and the political processes of diplomatic negotiations among the related states. It also considers the relevance of the handed-down legacies and lessons to the current Japanese international medical and health cooperation.